Mixed numerology OFDM design

ABSTRACT

Methods, systems, and devices are described for hierarchical communications and low latency support within a wireless communications system. An eNB and/or a UE may be configured to operate within the wireless communications system which is at least partially defined through a first layer with first layer transmissions having a first subframe type and a second layer with second layer transmissions having a second subframe type. The first subframe type may have a first round trip time (RTT) between transmission and acknowledgment of receipt of the transmission, and the second layer may have a second RTT that is less than the first RTT. Subframes of the first subframe type may be multiplexed with subframes of the second subframe type, such as through time division multiplexing. In some examples symbols of different duration may be multiplexed such that they different symbol durations coexist.

CROSS REFERENCES

The present Application for Patent claims priority to U.S. ProvisionalPatent Application No. 61/920,107 by Malladi et al., entitled “LTEHierarchical Burst Mode,” filed Dec. 23, 2013, assigned to the assigneehereof, and expressly incorporated by reference herein.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to techniques for hierarchical communications in wirelesscommunications systems.

A wireless communication network may include a number of base stationsthat can support communication for a number of mobile devices. A mobiledevice may communicate with a base station via downlink (DL) and uplink(UL) transmissions. The downlink (or forward link) refers to thecommunication link from the base station, such as an enhanced NodeB(eNB), to a mobile device, also referred to as a user equipment (UE).The uplink (or reverse link) refers to the communication link from themobile device to the base station.

Multiple access technologies may use Frequency Division Duplexing (FDD)or Time Division Duplexing (TDD) to provide uplink and downlinkcommunications over one or more carriers. TDD operation may providerelatively flexible deployments without requiring paired spectrumresources. TDD formats include transmission of frames of data, eachincluding a number of different subframes in which different subframesmay be uplink or downlink subframes. In systems that operate using TDD,different formats may be used in which uplink and downlinkcommunications may be asymmetric. FDD operation utilizes differentcarriers for concurrent uplink and downlink communications.

In some wireless communication networks, base stations and UEs maysupport operation on multiple carriers, which may be referred to ascarrier aggregation. Carrier aggregation may be used to increasethroughput between a base station supporting multiple component carriersand a mobile device, and mobile devices may be configured to communicateusing multiple component carriers associated with multiple basestations.

In some instances, transmission errors between mobile devices and basestations are avoided and/or corrected by utilizing an automatic repeatrequest (ARQ) scheme. An ARQ scheme may be employed to detect whether areceived packet is in error. For example, in an ARQ scheme, a receivermay notify a transmitter with a positive acknowledgment (ACK), when apacket is received free from errors; and the receiver may notify thetransmitter with a negative acknowledgment (NACK), if an error isdetected. A hybrid ARQ (HARQ) scheme may be used to correct some errorsand to detect and discard certain uncorrectable packets. In somescenarios, however, the overall HARQ delay may cause certaininefficiencies in wireless communications. Also, in some instances,mobile devices within a system may have varying latency requirements,and inefficient operation may be exacerbated for such devices.

SUMMARY

The described features generally relate to one or more improved systems,methods, and/or devices for hierarchical communications and low latencysupport within a wireless communications system. An eNB and/or a UE maybe configured to operate within the multi-layered wirelesscommunications system. The system may include first layer transmissionshaving a first subframe type and second layer transmissions having asecond subframe type. The first subframe type may have a first roundtrip time (RTT) between transmission and acknowledgment of receipt ofthe transmission, and the second layer may have a second RTT that isless than the first RTT. In some examples, subframes of the firstsubframe type may be multiplexed with subframes of the second subframetype, for example through time division multiplexing.

In some examples, an eNB and/or UE may transmit, in a frame, one or moresubframes having a first subframe type. Subframes of the first subframetype may be transmitted concurrently, on different carriers. The eNBand/or UE may also transmit, in the frame, a subframe of a secondsubframe type using one carrier. The carrier transmitting the secondsubframe type may have a bandwidth that is greater than the bandwidth ofthe first subframe type.

In still other examples, multiple symbol durations may coexist within asystem to account for varying latency requirements. Different regions ofa carrier may have different symbol durations, and the regions may bedynamically adjusted to account for changing latency demands of trafficwithin the system.

A method of wireless communication is described. The method may includeconfiguring a carrier with a first region having a first symbol durationand a second region having a second symbol duration different from thefirst symbol duration, where the first and second regions aretime-division multiplexed (TDM) or frequency-division multiplexed (FDM),and communicating with a user equipment (UE) using the first or secondregion based at least in part on a latency requirement of the UE.

An apparatus for wireless communication is also described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to configure a carrier with a firstregion having a first symbol duration and a second region having asecond symbol duration different from the first symbol duration, wherethe first and second regions are time-division multiplexed (TDM) orfrequency-division multiplexed (FDM), and communicate with a userequipment (UE) using the first or second region based at least in parton a latency requirement of the UE.

A further apparatus for wireless communication is also described. Theapparatus may include means for configuring a carrier with a firstregion having a first symbol duration and a second region having asecond symbol duration different from the first symbol duration, wherethe first and second regions are time-division multiplexed (TDM) orfrequency-division multiplexed (FDM), and means for communicating with auser equipment (UE) using the first or second region based at least inpart on a latency requirement of the UE.

A computer readable medium storing code for wireless communication isalso described. The code may include instructions executable toconfigure a carrier with a first region having a first symbol durationand a second region having a second symbol duration different from thefirst symbol duration, where the first and second regions aretime-division multiplexed (TDM) or frequency-division multiplexed (FDM),and communicate with a user equipment (UE) using the first or secondregion based at least in part on a latency requirement of the UE.

Some examples of the method, apparatuses, or computer-readable mediadescribed above may also include features, means, or instructions foradjusting a portion of the carrier occupied by the second region basedat least in part the latency requirement of the UE. In some examples,the first and second regions are TDM, and adjusting the portion of thecarrier occupied by the second region includes adjusting a time durationor periodicity of the second region. In other examples, the first andsecond regions are FDM, and adjusting the portion of the carrieroccupied by the second region includes adjusting a bandwidth of thesecond region. Further, some examples may include features, means, orinstructions for configuring a guard band between the first and secondregions. Additionally or alternatively, configuring the carrier mayinclude transmitting a signal in a symbol of the first region, thesignal indicative of the second symbol duration and it may include atleast one of radio resource control (RRC) signaling, a broadcastmessage, Layer 1 signaling, or a media access control (MAC) layersignaling.

Some examples of the method, apparatuses, or computer-readable mediadescribed above may also include features, means, or instructions forconfiguring a third region of the carrier, the third region having thesecond symbol duration, wherein the first and second regions are FDM,and wherein the third region is TDM with the first and second regions.Some examples may also include features, means, or instructions forconfiguring a guard band between the first and second regions. In someexamples, the second symbol duration is shorter than the first symbolduration.

A further method of wireless communication is also described. The methodmay include identifying a first region of a carrier, the first regionhaving a first symbol duration, identifying a second region of thecarrier, the second region having a second symbol duration differentfrom the first symbol duration, where the first and second regions aretime-division multiplexed (TDM) or frequency-division multiplexed (FDM),and communicating with a base station using the first or second regionbased at least in part on a latency requirement.

A further apparatus for wireless communication is also described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be executable by the processor to identify a firstregion of a carrier, the first region having a first symbol duration,identify a second region of the carrier, the second region having asecond symbol duration different from the first symbol duration, wherethe first and second regions are time-division multiplexed (TDM) orfrequency-division multiplexed (FDM), and communicate with a basestation using the first or second region based at least in part on alatency requirement.

A further apparatus for wireless communication is also described. Theapparatus may include means for identifying a first region of a carrier,the first region having a first symbol duration, means for identifying asecond region of the carrier, the second region having a second symbolduration different from the first symbol duration, where the first andsecond regions are time-division multiplexed (TDM) or frequency-divisionmultiplexed (FDM), and means for communicating with a base station usingthe first or second region based at least in part on a latencyrequirement.

A further computer-readable medium storing code for wirelesscommunication is also described. The code may include instructionsexecutable to identify a first region of a carrier, the first regionhaving a first symbol duration, identify a second region of the carrier,the second region having a second symbol duration different from thefirst symbol duration, where the first and second regions aretime-division multiplexed (TDM) or frequency-division multiplexed (FDM),and communicate with a base station using the first or second regionbased at least in part on a latency requirement.

In some examples of the methods, apparatus, or computer-readable mediadescribed above, the first and second regions are FDM, and the method,apparatus, or computer-readable medium may include features, means, orinstructions for identifying a guard band between the first and secondregions. In some examples, identifying the second region of the carrierincludes receiving a signal in a symbol of the first region, the signalindicative of the second symbol duration and may include at least one ofradio resource control (RRC) signaling, a broadcast message, Layer 1signaling, or a media access control (MAC) layer signaling.

Some examples may also include features, means, or instructions foridentifying a third region of the carrier, the third region having thesecond symbol duration, where the first and second regions are FDM andwhere the third region is TDM with the first and second regions.Additionally or alternatively, some examples include features, means, orinstructions for identifying a guard band between the first and secondregions. In some examples, the second symbol duration is shorter thanthe first symbol duration.

Further scope of the applicability of the described methods andapparatuses will become apparent from the following detaileddescription, claims, and drawings. The detailed description and specificexamples are given by way of illustration only, since various changesand modifications within the spirit and scope of the description willbecome apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the following drawings. In theappended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows a block diagram conceptually illustrating an example of atelecommunications system, in accordance with an aspect of the presentdisclosure;

FIG. 2 is a diagram illustrating an example of a downlink framestructure that may be used in a wireless communication system, inaccordance with an aspect of the present disclosure;

FIG. 3A is a block diagram conceptually illustrating an example of aradio frame and different subframes that may be transmitted on differentlayers of a wireless communication system, in accordance with an aspectof the present disclosure;

FIG. 3B is a block diagram conceptually illustrating an example of aradio frame and different subframes that may be transmitted on differentlayers of a wireless communication system, in accordance with an aspectof the present disclosure;

FIG. 3C is a block diagram conceptually illustrating an example of acarrier of a wireless communication system with symbols having differentsymbol durations time-division multiplexed, in accordance with an aspectof the present disclosure;

FIG. 3D is a block diagram conceptually illustrating an example of acarrier of a wireless communication system with symbols having differentsymbol durations frequency-division multiplexed, in accordance with anaspect of the present disclosure;

FIG. 3E is a block diagram conceptually illustrating an example of acarrier of a wireless communication system with symbols having differentsymbol durations time-division multiplexed and frequency-divisionmultiplexed, in accordance with an aspect of the present disclosure;

FIG. 4 is a block diagram conceptually illustrating an example of aradio frame and transmission acknowledgment timing for differentsubframes that may be transmitted on different layers of a wirelesscommunication system, in accordance with an aspect of the presentdisclosure;

FIG. 5 is a block diagram conceptually illustrating another example of aradio frame and different subframes that may be transmitted on differentlayers of a wireless communication system, in accordance with an aspectof the present disclosure;

FIG. 6 is a block diagram conceptually illustrating another example of aradio frame and different subframes that may be transmitted on differentlayers of a wireless communication system, in accordance with an aspectof the present disclosure;

FIG. 7 is a block diagram conceptually illustrating a portion of awireless communications system that may utilize carrier aggregation, inaccordance with aspects of the present disclosure;

FIG. 8A is a block diagram conceptually illustrating an example of radioframes for different component carriers and scalable bandwidth subframesthat may transmitted on different layers of a wireless communicationsystem, in accordance with an aspect of the present disclosure;

FIG. 8B is a block diagram conceptually illustrating an example of radioframes for different component carriers and scalable bandwidth subframesthat may transmitted on different layers of a wireless communicationsystem, in accordance with an aspect of the present disclosure;

FIG. 9 is a block diagram conceptually illustrating another example ofradio frames for different component carriers and scalable bandwidthsubframes that may transmitted on different layers of a wirelesscommunication system, in accordance with an aspect of the presentdisclosure;

FIG. 10 is a block diagram conceptually illustrating another example ofradio frames for different component carriers and scalable bandwidthsubframes that may transmitted on different layers of a wirelesscommunication system, in accordance with an aspect of the presentdisclosure;

FIGS. 11A and 11B are block diagrams conceptually illustrating devices,such as eNBs or UEs, for use in wireless communications in accordancewith aspects of the present disclosure;

FIG. 12 is a block diagram conceptually illustrating a design of an eNB,in accordance with aspects of the present disclosure;

FIG. 13 is a block diagram conceptually illustrating a design of a UE,in accordance with aspects of the present disclosure;

FIG. 14 is a block diagram conceptually illustrating a transceivermodule of an eNB or UE, for use in wireless communications in accordancewith aspects of the present disclosure;

FIG. 15 is a block diagram conceptually illustrating an example of a UEand an eNB, in accordance with aspects of the present disclosure;

FIG. 16 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure;

FIG. 17 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure;

FIG. 18 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure;

FIG. 19 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure;

FIG. 20 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure; and

FIG. 21 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure.

DETAILED DESCRIPTION

Techniques are described for hierarchical communications within awireless communications system. Also described are techniques forcommunicating with orthogonal frequency-division multiplexing (OFDM)symbols of different duration. This may be referred to as mixed OFDMnumerology. An eNB and/or a UE, according to various examples, may beconfigured to operate within the wireless communications system which ispartially defined through multiple hierarchical layers or which isconfigured with mixed OFDM numerology. A first hierarchical layer maysupport first layer transmissions with a first subframe type, and asecond hierarchical layer may support second layer transmissions with asecond subframe type. In some examples, as mentioned above, receiversmay acknowledge receipt of a transmission by providing a positiveacknowledgment (ACK) or negative acknowledgment (NACK) of thetransmission through, for example, a HARQ scheme. Receivers operating inthe first layer may, in examples, acknowledge receipt of a transmissionin a subframe following the subframe in which the transmission wasreceived. Receivers operating in the second layer may, in examples,acknowledge receipt of a transmission in a same subframe as the subframein which the transmission was received. The time required to transmit anACK/NACK and receive a retransmission may be referred to as round triptime (RTT), and subframes of the second subframe type may have a secondRTT that is shorter than a RTT for subframes of the first subframe type.

In such examples, a latency for receivers operating in the second layermay be reduced relative to latency of the first layer. Reduced latencymay provide for enhanced data transfer rates, in some examples, throughrelatively fast ACK/NACK and any necessary retransmissions. For example,Transmission Control Protocol (TCP) may be used to provide a reliable,ordered, and error-checked delivery of a stream of data between atransmitter and a receiver. TCP can have relatively stringentrequirements for TCP segment error rates, and this impact is even moresignificant as data rates are increased. In order to achieve desired TCPsegment error rates, packets may need to be retransmitted one or moretimes. The latency for ACK/NACK and retransmission may thus impact thetime that it may take to achieve the TCP segment error rate, and maythus reduce the overall data rate that is achievable. Thus, reducedlatency for such acknowledgments and retransmissions may reduce the timeto achieve TCP segment error rates and may thereby allow enhanced datarates. Accordingly, receivers operating in the second hierarchicallayer, either exclusively or in combination with operation in the firsthierarchical layer, may support enhanced data rates relative toreceivers operating exclusively in the first hierarchical layer.

In some further examples, an eNB and/or UE may concurrently transmit,within a frame, one or more subframes having a first subframe type usingtwo or more separate carriers, and transmit, within the frame, asubframe of a second subframe type using one carrier. One or more of thecarriers transmitting the first subframe type may have a firstbandwidth, and the carrier transmitting the second subframe type mayhave a second bandwidth that is greater than the first bandwidth. Insome examples, the first bandwidth may be 20 MHz, and the secondbandwidth may be 40 MHz, 80 MHz, or 160 MHz. In some examples, scalablebandwidth for subframes of the second subframe type may be combined withshorter RTTs such as described above, to provide enhanced data rates.

In still other examples, an eNB may configure and/or a UE may identify,several regions of a carrier having different symbol durations. Forinstance, a carrier may be configured with a region having a longersymbol duration (e.g., 15 kHz subcarrier spacing) to support typicalcommunications traffic, and the carrier may be configured with a regionhaving a shorter symbol duration (e.g., 60 kHz subcarrier spacing) toserve low latency traffic. In some examples, a system may operate with alonger symbol duration by default, and the system may configure regionswith shorter symbol duration on demand. While in other cases, a systemmay operate with a shorter symbol duration, and it may configure regionswith longer symbol duration on demand. The default operation may bedepend on traffic within the system, or may depend on particular goalsof the system operator.

In some cases, a longer symbol duration may be advantageous. Forexample, for a given cyclic prefix length, a longer symbol duration mayresult in lower cyclic prefix overhead. A longer symbol duration maythus provide for better spectral efficiency than a shorter symbolduration. Nonetheless, shorter symbol duration may be desirable for lowlatency traffic. In addition to the HARQ advantages mentioned above, ashorter symbol duration may mean that each symbol contains fewersubcarriers, which, in turn, may result in shorter transmission,processing, decoding, or response times for devices within the system. Asystem may thus configure regions of shorter symbol duration on demandfor low latency traffic.

The portions of a carrier configured for longer or short symbolduration—e.g., the portions of a carrier having a long symbol durationby default and configured with short-symbol-duration regions—may beadjusted. In the case of TDM, this adjustment may include adjustingduration or periodicity. For FDM, the adjustment may be a bandwidthadjustment.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, andother systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc.UTRA and E-UTRA are part of Universal Mobile Telecommunication System(UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, andGSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. The description below, however, describes an LTEsystem for purposes of example, and LTE terminology is used in much ofthe description below, although the techniques are applicable beyond LTEapplications.

Thus, the following description provides examples, and is not limitingof the scope, applicability, or configuration set forth in the claims.Changes may be made in the function and arrangement of elementsdiscussed without departing from the spirit and scope of the disclosure.Various examples may omit, substitute, or add various procedures orcomponents as appropriate. For instance, the methods described may beperformed in an order different from that described, and various stepsmay be added, omitted, or combined. Also, features described withrespect to certain examples may be combined in other examples.

Referring first to FIG. 1, a diagram illustrates an example of awireless communications system 100, in accordance with an aspect of thepresent disclosure. The wireless communications system 100 includes aplurality of access points (e.g., base stations, eNBs, or WLAN accesspoints) 105, a number of user equipment (UEs) 115, and a core network130. Some of the access points 105 may communicate with the UEs 115under the control of a base station controller (not shown), which may bepart of the core network 130 or the certain access points 105 (e.g.,base stations or eNBs) in various examples. Access points 105 maycommunicate control information and/or user data with the core network130 through backhaul links 132. In examples, the access points 105 maycommunicate, either directly or indirectly, with each other overbackhaul links 134, which may be wired or wireless communication links.The wireless communications system 100 may support operation on multiplecarriers (waveform signals of different frequencies). Multi-carriertransmitters can transmit modulated signals simultaneously on themultiple carriers. For example, each communication link 125 may be amulti-carrier signal modulated according to the various radiotechnologies described above. Each modulated signal may be sent on adifferent carrier and may carry control information (e.g., referencesignals, control channels, etc.), overhead information, data, etc.

In some examples, at least a portion of the wireless communicationssystem 100 may be configured to operate on multiple hierarchical layersin which one or more of the UEs 115 and one or more of the access points105 may be configured to support transmissions on a hierarchical layerthat has a reduced latency with respect to another hierarchical layer.In some examples a hybrid UE 115-a may communicate with access point105-a on both a first hierarchical layer that supports first layertransmissions with a first subframe type and a second hierarchical layerthat supports second layer transmissions with a second subframe type.For example, access point 105-a may transmit subframes of the secondsubframe type that are time division duplexed with subframes of thefirst subframe type.

In some examples, hybrid UE 115-a may acknowledge receipt of atransmission by providing ACK/NACK for the transmission through, forexample, a HARQ scheme. Acknowledgments from hybrid UE 115-a fortransmissions in the first hierarchical layer may be provided, in someexamples, after a predefined number of subframes following the subframein which the transmission was received. The hybrid UE 115-a, whenoperating in the second hierarchical layer may, in examples, acknowledgereceipt in a same subframe as the subframe in which the transmission wasreceived. The time required to transmit an ACK/NACK and receive aretransmission may be referred to as round trip time (RTT), and thussubframes of the second subframe type may have a second RTT that isshorter than a RTT for subframes of the first subframe type.

In other examples, a second layer UE 115-b may communicate with accesspoint 105-b on the second hierarchical layer only. Thus, hybrid UE 115-aand second layer UE 115-b may belong to a second class of UEs 115 thatmay communicate on the second hierarchical layer, while legacy UEs 115may belong to a first class of UEs 115 that may communicate on the firsthierarchical layer only. Access point 105-b and UE 115-b may communicateon the second hierarchical layer through transmissions of subframes ofthe second subframe type. Access point 105-b may transmit subframes ofthe second subframe type exclusively, or may transmit one or moresubframes of the first subframe type on the first hierarchical layerthat are time division multiplexed with subframes of the second subframetype. Second layer UE 115-b, in the event that access point 105-btransmits subframes of the first subframe type, may ignore suchsubframes of the first subframe type. Thus, second layer UE 115-b mayacknowledge receipt of transmissions in a same subframe as the subframein which the transmissions are received. Thus, second layer UE 115-b mayoperate with reduced latency compared to UEs 115 that operate on thefirst hierarchical layer.

Additionally or alternatively, the system may be configured with acarrier or carriers having regions with different, co-existing symbolduration. For instance, a carrier may be configured with a first regionhaving a first symbol duration and second region having a second symbolduration. The regions may be TDM or FDM. An access point 105 maycommunicate with UEs 115 using the first or second region, or both,depending on a latency requirement of the UE 115.

The access points 105 may wirelessly communicate with the UEs 115 viaone or more access point antennas. Each of the access points 105 sitesmay provide communication coverage for a respective coverage area 110.In some examples, access points 105 may be referred to as a basetransceiver station, a radio base station, a radio transceiver, a basicservice set (BSS), an extended service set (ESS), a NodeB, eNodeB, HomeNodeB, a Home eNodeB, or some other suitable terminology. The coveragearea 110 for a base station may be divided into sectors making up only aportion of the coverage area (not shown). The wireless communicationssystem 100 may include access points 105 of different types (e.g.,macro, micro, and/or pico base stations). The access points 105 may alsoutilize different radio technologies, such as cellular and/or WLAN radioaccess technologies. The access points 105 may be associated with thesame or different access networks or operator deployments. The coverageareas of different access points 105, including the coverage areas ofthe same or different types of access points 105, utilizing the same ordifferent radio technologies, and/or belonging to the same or differentaccess networks, may overlap.

In LTE/LTE-A network communication systems, the terms evolved Node B(eNodeB or eNB) may be generally used to describe the access points 105.The wireless communications system 100 may be a Heterogeneous LTE/LTE-Anetwork in which different types of access points provide coverage forvarious geographical regions. For example, each access point 105 mayprovide communication coverage for a macro cell, a pico cell, a femtocell, and/or other types of cell. Small cells such as pico cells, femtocells, and/or other types of cells may include low power nodes or LPNs.A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEs115 with service subscriptions with the network provider. A small cellwould generally cover a relatively smaller geographic area and may allowunrestricted access by UEs 115 with service subscriptions with thenetwork provider, for example, and in addition to unrestricted access,may also provide restricted access by UEs 115 having an association withthe small cell (e.g., UEs in a closed subscriber group (CSG), UEs forusers in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB. An eNB may support one or multiple (e.g., two,three, four, and the like) cells.

The core network 130 may communicate with the eNBs or other accesspoints 105 via a backhaul 132 (e.g., S1 interface, etc.). The accesspoints 105 may also communicate with one another, e.g., directly orindirectly via backhaul links 134 (e.g., X2 interface, etc.) and/or viabackhaul links 132 (e.g., through core network 130). The wirelesscommunications system 100 may support synchronous or asynchronousoperation. For synchronous operation, the access points 105 may havesimilar frame timing, and transmissions from different access points 105may be approximately aligned in time. For asynchronous operation, theaccess points 105 may have different frame timing, and transmissionsfrom different access points 105 may not be aligned in time.Furthermore, transmissions in the first hierarchical layer and secondhierarchical layer may or may not be synchronized among access points105. The techniques described herein may be used for either synchronousor asynchronous operations.

The UEs 115 are dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to by those skilled in the art as a mobile station, asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a wireless device, a wirelesscommunications device, a remote device, a mobile subscriber station, anaccess terminal, a mobile terminal, a wireless terminal, a remoteterminal, a handset, a user agent, a mobile client, a client, or someother suitable terminology. A UE 115 may be a cellular phone, a personaldigital assistant (PDA), a wireless modem, a wireless communicationdevice, a handheld device, a tablet computer, a laptop computer, acordless phone, a wearable item such as a watch or glasses, a wirelesslocal loop (WLL) station, or the like. A UE 115 may be able tocommunicate with macro eNodeBs, small cell eNodeBs, relays, and thelike. A UE 115 may also be able to communicate over different accessnetworks, such as cellular or other WWAN access networks, or WLAN accessnetworks.

The communication links 125 shown in wireless communications system 100may include uplink (UL) transmissions from a UE 115 to an access point105, and/or downlink (DL) transmissions, from an access point 105 to aUE 115. The downlink transmissions may also be called forward linktransmissions while the uplink transmissions may also be called reverselink transmissions. The communications links 125 may carry transmissionsof each hierarchical layer which, in some examples, may be multiplexedin the communications links 125. The UEs 115 may be configured tocollaboratively communicate with multiple access points 105 through, forexample, Multiple Input Multiple Output (MIMO), carrier aggregation(CA), Coordinated Multi-Point (CoMP), or other schemes. MIMO techniquesuse multiple antennas on the access points 105 and/or multiple antennason the UEs 115 to transmit multiple data streams. Carrier aggregationmay utilize two or more component carriers on a same or differentserving cell for data transmission. CoMP may include techniques forcoordination of transmission and reception by a number of access points105 to improve overall transmission quality for UEs 115 as well asincreasing network and spectrum utilization.

As mentioned, in some examples access points 105 and UEs 115 may utilizecarrier aggregation to transmit on multiple carriers. In some examples,access points 105 and UEs 115 may concurrently transmit in a firsthierarchical layer, within a frame, one or more subframes each having afirst subframe type using two or more separate carriers. Each carriermay have a bandwidth of, for example, 20 MHz, although other bandwidthsmay be utilized. Hybrid UE 115-a, and/or second layer UE 115-b may, incertain examples, receive and/or transmit one or more subframes in asecond hierarchical layer utilizing a single carrier that has abandwidth greater than a bandwidth of one or more of the separatecarriers. For example, if four separate 20 MHz carriers are used in acarrier aggregation scheme in the first hierarchical layer, a single 80MHz carrier may be used in the second hierarchical layer. The 80 MHzcarrier may occupy a portion of the radio frequency spectrum that atleast partially overlaps the radio frequency spectrum used by one ormore of the four 20 MHz carriers. In some examples, scalable bandwidthfor the second hierarchical layer type may be combined techniques toprovide shorter RTTs such as described above, to provide furtherenhanced data rates.

Each of the different operating modes that may be employed by wirelesscommunication system 100 may operate according to frequency divisionduplexing (FDD) or time division duplexing (TDD). In some examples,different hierarchical layers may operate according to different TDD orFDD modes. For example, a first hierarchical layer may operate accordingto FDD while a second hierarchical layer may operate according to TDD.In some examples, OFDMA communications signals may be used in thecommunications links 125 for LTE downlink transmissions for eachhierarchical layer, while single carrier frequency division multipleaccess (SC-FDMA) communications signals may be used in thecommunications links 125 for LTE uplink transmissions in eachhierarchical layer. Additional details regarding implementation ofhierarchical layers in a system such as the wireless communicationssystem 100, as well as other features and functions related tocommunications in such systems, are provided below with reference toFIGS. 2-19.

FIG. 2 is a diagram illustrating an example of a downlink framestructure 200 that may be used in a wireless communication system,including the wireless communication system 100 described above withreference to the FIG. 1. For example, the frame structure 200 may beused in LTE/LTE-A or similar systems. A frame 210 (10 ms) may be dividedinto 10 equally sized subframes (e.g., subframe 225, 230, etc.). In someexamples, frame 210 may be used for transmissions of both a firsthierarchical layer and a second hierarchical layer, with one or moresubframes within frame 210 used for transmissions of the firsthierarchical layer and one or more other subframes within frame 210 usedfor transmissions of the second hierarchical layer. For example,subframes 225 and 230 may be used for transmissions of the firsthierarchical layer, and subframes 235, 240, and 245 may be used fortransmissions of the second hierarchical layer. The first hierarchicallayer in certain examples may correspond to a legacy LTE/LTE-A layer,and second hierarchical layer may correspond to a low latency layer.

In examples where the first hierarchical layer corresponds to a legacyLTE/LTE-A layer, first layer subframes may include two consecutive timeslots 262 and 264. An OFDMA component carrier 250 may be illustrated asa resource grid representing the two time slots 262, 264, each time slotincluding seven OFDM symbols 266, for a normal cyclic prefix. Theresource grid may be divided into multiple resource elements 252. Inlegacy LTE/LTE-A, a resource block 256 may contain 12 consecutivesubcarriers 268 in the frequency domain and, for a normal cyclic prefixin each OFDM symbol 266, 7 consecutive OFDM symbols 266 in the timedomain, or 84 resource elements 252. The tone spacing for subcarriers268 may be 15 kHz, and a useful symbol duration for OFDM symbols 266 maybe 66.67 μs. As compared with other symbol duration that may beconfigured within the system, the symbol duration for OFDM symbols 266may represent a longer symbol duration. OFDM symbols 266 may alsoinclude a cyclic prefix that is, for a normal legacy LTE cyclic prefix,5.1 μs for a first OFDM symbol 266 in each slot 262, 264, or 4.69 μs forother OFDM symbols 266. As noted, in examples where the secondhierarchical layer corresponds to a low latency layer, low latency orburst subframes may replace a number of the downlink subframes (and maybe of the same duration). Burst subframes, according to some examples,may include more symbols within the subframe, and each symbol may have areduced symbol duration relative to the legacy OFDM (or SC-FDM) symbols266. Burst mode symbols also may have increased tone spacing forsubcarriers relative to legacy symbols, and in some examples have a tonespacing of 120 kHz. Additionally or alternatively, frame structure 210may coexist, e.g., in the same hierarchical layer, with other regions ofa carrier having shorter symbol duration. More detailed examples will bedescribed with reference to FIGS. 3A-10.

Some of the resource elements, designated R (e.g., 254), may include DLreference signals (DL-RS). The DL-RS may include Cell-specific RS (CRS)(also sometimes called common RS) and UE-specific RS (UE-RS). UE-RS maybe transmitted only on the resource blocks upon which the correspondingphysical DL shared channel (PDSCH) 260 is mapped. The number of bitscarried by each resource element may depend on the modulation scheme.

As illustrated in FIG. 2, a physical downlink control channel (PDCCH)255 may be time-division multiplexed with a physical downlink sharedchannel (PDSCH) 260 and may be fully distributed within the entirebandwidth of the component carrier 250 within a first region of firstlayer subframe 230. In the example illustrated in FIG. 2, PDCCH 255takes up the first three symbols of the subframe 230. PDCCH 255 may havemore or fewer symbols as is appropriate based on the component carrierbandwidth and amount of control information for the subframe 230.

The PDCCH may carry downlink control information (DCI) in controlchannel elements (CCEs). The DCI may include, for example, informationregarding the downlink scheduling assignments, uplink resource grants,transmission scheme, uplink power control, hybrid automatic returnrepeat request (HARM) information, modulation and coding schemes (MCS)and other information. In some examples, the DCI may include informationfor each hierarchical layer. In other examples, subframes of differentsubframe types may include DCI for different hierarchical layers. A DCIcan be UE-specific (dedicated) or cell-specific (common) and placed indifferent dedicated and common search spaces within the PDCCH dependingon the format of the DCI.

In various examples, acknowledgement/negative acknowledgement (ACK/NACK)for downlink transmissions may be performed by Hybrid ARQAcknowledgement (HARQ-ACK) using a physical uplink control channel(PUCCH). PUCCH resources for HARQ-ACK may be determined based on when adownlink transmission is received. In some examples, HARQ-ACK may betransmitted in PUCCH resources based on a subframe k in which thedownlink transmission is received. For legacy FDD operation, in certainexamples, HARQ-ACK for downlink transmissions may be reported in a PUCCHsubframe determined based on the downlink subframe (e.g., k+4). Forlegacy TDD operation, HARQ-ACK may be provided in a first availableuplink subframe following a certain time period from the downlinksubframe k (e.g., the first available subframe k+4 or after). Inexamples where the first hierarchical layer corresponds to a legacyLTE/LTE-A layer, HARQ-ACK may take several milliseconds. In exampleswhere the second hierarchical layer corresponds to a low latency layer(as will be described in more detail with reference to FIGS. 3A-10), theRTT for acknowledgment may be significantly reduced (e.g., to within asubframe). While the example of FIG. 2 is described with respect todownlink transmissions, similar structures and timing may be used inuplink transmissions which, in some examples, may be transmitted usingSC-FDMA symbols.

As discussed above, various examples provide communications in awireless communications system, such as wireless communications system100 of FIG. 1, according to multiple hierarchical layers. Communicationsin a first hierarchical layer may use the frame structure, slots,symbols and subcarrier spacing such as described above with respect toFIG. 2, and communications in a second hierarchical layer may usesymbols having a reduced symbol duration. FIG. 3A is a block diagram300-a conceptually illustrating an example of radio frames and differentsubframes that may be transmitted on different layers of a wirelesscommunication system, in accordance with an aspect of the presentdisclosure. The radio frames of FIG. 3A may be transmitted usingportions of the wireless communications system 100 described withreference to FIG. 1 between one or more access points 105 and one ormore UEs 115, for example. In this example, a legacy TDD frame 310 mayinclude ten 1 ms subframes that include downlink subframes 325, specialsubframes 330, and uplink subframes 335. The downlink subframes 325,special subframes 330, and uplink subframes 335 may include a subframestructure as discussed above with respect to FIG. 2, including 14symbols 366 within each 1 ms subframe. In some examples, downlinksubframes 325 may include downlink OFDM symbols, uplink subframes mayinclude SC-FDM symbols, and special subframes 330 may include bothuplink SC-FDM symbols and downlink OFDM symbols.

In the example of FIG. 3A, low latency or burst mode frame 320 mayreplace a number of the downlink subframes 325 with burst subframes 340.Burst subframes 340, according to some examples, may be transmitted in adifferent hierarchical layer than downlink subframes 325, specialsubframes 330, and uplink subframes 335. Burst subframes 340, inexamples, may include 88 symbols (although, as discussed herein, manydifferent symbol variations may be used in other examples). In theexample of FIG. 3A, burst subframes 340 may be TDD burst subframes andmay include downlink symbols 345, special symbols 350, and uplinksymbols 355. Each of the symbols 345, 350, and 355 may have a reducedsymbol duration relative to the legacy OFDM or SC-FDM symbols (e.g.,symbols 266 of FIG. 2), and in some examples have a symbol duration of11.36 μs per symbol, including a useful symbol duration of 8.33 μs and acyclic prefix duration of 3.03 μs. The symbols 345, 350, or 355 may thusrepresent a shorter symbol duration as compared to other symboldurations configured with the system. Symbols 345, 350, and 355 may haveincreased tone spacing for subcarriers relative to legacy symbols, andin some examples have a tone spacing of 60 or 120 kHz. In some examples,a hybrid UE, second layer UE, and/or eNB may generate legacy symbols 366utilizing a single internal clock configured to generate legacy symbols366 having a first symbol duration, and may generate the symbols 345,350, 355 of burst subframes by adapting the clock to generate symbols345, 350, 355 having a second symbol duration. In other examples,separate clocks may be used to generate legacy symbols 366 and thesymbols 345, 350, 355 of burst subframes.

Symbols 345, 350, and 355 may include control channels and sharedchannels similarly as discussed with respect to FIG. 2, which may beincluded within symbols or across symbols. In some examples, hybrid UEs(e.g., UE 115-a of FIG. 1) may be configured to communicate using bothlegacy subframes 325, 330, 335, and burst subframes 340. Likewise,second layer UEs (e.g., UE 115-b of FIG. 1) may be configured tocommunicate using only burst subframes 340, and legacy UEs may beconfigured to communicate using only legacy subframes 325, 330, 335. Inexamples where a UE may communicate on just one hierarchical layer,subframes of the other hierarchical layer(s) may be ignored.

In the example of FIG. 3A, frame 320 includes three burst subframes 340,although this may increase or decrease based on system requirements,current demands of the system, and/or one or more other factors. Forexample, an eNB (such as access point 105 of FIG. 1) may determine thatno UEs are within its coverage area that may be configured for operationon the second hierarchical layer, and thus not transmit any burstsubframes 340. In other cases, an eNB may determine that a relativelylarge number of UEs are in its coverage area and may configure arelatively large number of subframes as burst subframes 340. In somecases, an eNB may transmit burst subframes exclusively. Suchconfigurations may be set by a carrier, may be semi-static, or may bedynamically changed based on conditions of the wireless communicationssystem at a given time.

FIG. 3B is a block diagram 300-b conceptually illustrating an example ofa radio frame and different subframes that may be transmitted ondifferent layers of a wireless communication system, in accordance withan aspect of the present disclosure. The radio frames of FIG. 3B may betransmitted using portions of the wireless communications system 100described with reference to FIG. 1 between one or more access points 105and one or more UEs 115, for example. FIG. 3B may include burst modeframe 320-a, which may include downlink subframes 325-a, specialsubframes 330-a, and uplink subframes 335-a similar to downlinksubframes 325, special subframes 330, and uplink subframes 335 asdescribed above with reference to FIG. 3A. Additionally, burst modeframe 320-a may replace a number of subframes with burst subframes 360.

In the example of FIG. 3B, burst subframes 360 may include a number offrequency bands, such as downlink frequency bands 370 or uplinkfrequency bands 375. Burst subframes 360 may be similar to the burstsubframes 340 of FIG. 3A, in that burst subframes 360 may be transmittedin a different hierarchical layer than downlink subframes 325-a, specialsubframes 330-a, and uplink subframes 335-a. Burst subframes 360 may befrequency division multiplexed with other subframes of the burst modeframe 320-a. In some examples, burst subframes 360 may be referred to asFDD burst subframes, in a manner similar to the TDD burst subframesdescribed above with reference to FIG. 3A; and they may include bothdownlink frequency bands 370 and uplink frequency bands 375.

Each of the downlink frequency bands 370 and uplink frequency bands 375may be made up of one or more subcarriers. In some examples, thefrequency bands 370 or 375 may span 14 symbols, or 88 symbols, dependingon the duration of the symbol period; but the frequency bands 370 and375 may span any number of symbols. Each downlink frequency band 370 anduplink frequency band 375 may include control channels and sharedchannels similar to those discussed with respect to FIG. 2, which may beincluded within symbols or across symbols. In some examples, hybrid UEs(e.g., UE 115-a of FIG. 1) may be configured to communicate using bothlegacy subframes 325-a, 330-a, 335-a, and burst subframes 360. Likewise,second layer UEs (e.g., UE 115-b of FIG. 1) may be configured tocommunicate using only burst subframes 360, and legacy UEs may beconfigured to communicate using only legacy subframes 325, 330, 335. Inexamples where a UE may communicate on just one hierarchical layer,subframes of the other hierarchical layer(s) may be ignored.

In some examples, the frequency bands 370 and 375 may use constant(e.g., predetermined), semi-static, or dynamically changed portions offrequency spectrum, which may be based on channel conditions or a numberof UEs within a coverage area. As discussed above with reference to FIG.3A, an eNB may vary the number of burst subframes transmitted, or maytransmit burst subframes exclusively.

Next, FIG. 3C is a block diagram conceptually illustrating an example ofa carrier 300-c of a wireless communication system with symbols havingdifferent symbol durations time-division multiplexed, in accordance withan aspect of the present disclosure. The carrier 300-c may betransmitted using portions of the wireless communications system 100described with reference to FIG. 1 between one or more access points 105and one or more UEs 115, for example.

The carrier 300-c may include a region 380-a having a longer symbolduration and a second region 385-a having a shorter symbol duration. Asdescribed above, the symbol duration of regions 380-a and 385-a may belonger or shorter relative to one another. So, for example, region 380-amay have symbols having a useful symbol duration of 66.67 μs, whileregion 385-a may have symbols having a useful symbol duration of 8.33μs. As depicted in the example of FIG. 3C, the regions 380-a and 385-amay be TDM. The carrier 300-c may include additional regions, which maylikewise be TDM.

The portion of the carrier 300-c occupied by the region 380-a or theregion 385-a may be adjusted according to a latency requirement of a UE115 (FIG. 1) served by the carrier 300-c. In the case of carrier 300-c,in which the regions 380-a and 385-a are TDM, this adjusting may includeadjusting a time duration or a periodicity of either region 380-a or385-a. In some examples, a signal transmitted in a symbol of the region380-a indicates the symbol duration of the region 385-a. That is, insome cases, a UE 115 receives, in a symbol of region 380-a, RRCsignaling, a broadcast message, Layer 1 signaling, MAC signaling, or thelike, that configures the region 385-a. This signaling may be utilizedto create, modify, or remove region 385-a, for example.

FIG. 3D is a block diagram conceptually illustrating an example of acarrier 300-d of a wireless communication system with symbols havingdifferent symbol durations frequency-division multiplexed, in accordancewith an aspect of the present disclosure. The carrier 300-c may, forexample, be transmitted using portions of the wireless communicationssystem 100 described with reference to FIG. 1 between one or more accesspoints 105 and one or more UEs 115.

The carrier 300-d may include a region 380-b having a longer symbolduration and a second region 385-b having a shorter symbol duration. Asdescribed above, the symbol duration of regions 380-b and 385-b may belonger or shorter relative to one another. In the example of FIG. 3D,the regions 380-b and 385-b may be FDM. The carrier 300-d may alsoinclude a guard band 390-a between the regions 380-b and 385-b. Theguard band 390-a may be a portion of spectrum that is not used by foruplink or downlink transmissions, and may help reduce interference fordevices communicating in regions 380-b or 385-b. The carrier 300-d mayinclude additional regions, which may likewise be FDM, or they may beTDM.

The portion of the carrier 300-d occupied by the region 380-b or theregion 385-b may be adjusted according to a latency requirement of a UE115 (FIG. 1) served by the carrier 300-d. For carrier 300-d, in whichthe regions 380-b and 385-b are FDM, adjusting may include adjusting abandwidth of either region 380-b or 385-b. A signal transmitted in asymbol of the region 380-b may indicate the bandwidth or symbolduration, or both, of the region 385-b. That is, in some cases, a UE 115receives, in a symbol of region 380-a, RRC signaling, a broadcastmessage, Layer 1 signaling, MAC signaling, or the like, that configuresthe region 385-b.

FIG. 3E is a block diagram conceptually illustrating an example of acarrier 300-e of a wireless communication system with symbols havingdifferent symbol durations time-division multiplexed andfrequency-division multiplexed, in accordance with an aspect of thepresent disclosure. The carrier 300-e may, for example, be transmittedusing portions of the wireless communications system 100 described withreference to FIG. 1 between one or more access points 105 and one ormore UEs 115.

The carrier 300-e may include a region 380-c having a longer symbolduration and a second region 385-c having a shorter symbol duration. Thesymbol duration of regions 380-c and 385-c may, as described above, belonger or shorter relative to one another. In the example of FIG. 3E,the regions 380-c and 385-c may be FDM; and the carrier 300-e may alsoinclude a guard band 390-b between the regions 380-c and 385-c. Thecarrier 300-d may include additional regions, which may likewise be FDM,or they may be TDM. In some examples, the carrier 300-e includes aregion 395 TDM with regions 380-c and 385-c. The region 395 may have asymbol duration that is the same as the symbol duration of region 385-c.Or, the region 395 may be configure with a symbol duration that isdifferent from both the regions 380-c and 385-c.

The portions of the carrier 300-e occupied by regions 380-c, 385-c, or390 may be adjusted according to the latency requirements of a UE 115(FIG. 1). This may include adjusting a bandwidth, a duration, or aperiodicity.

As mentioned above, a second hierarchical layer in a wirelesscommunications system, such as wireless communication system 100 of FIG.1 for example, may have lower latency as compared to a firsthierarchical layer. FIG. 4 is a block diagram 400 conceptuallyillustrating an example of a radio frames and transmissionacknowledgment timing for different subframes that may be transmitted ondifferent hierarchical layers of a wireless communication system, inaccordance with an aspect of the present disclosure. The radio frames ofFIG. 4 may be transmitted using portions of the wireless communicationssystem 100 described with reference to FIG. 1 between one or more accesspoints 105 and one or more UEs 115, for example. In this example,similarly as described with respect to FIG. 3A, a legacy TDD frame 410may include ten 1 ms subframes that include downlink subframes 425,special subframes 430, and uplink subframes 435. The downlink subframes425, special subframes 430, and uplink subframes 435 may include asubframe structure as discussed above with respect to FIG. 2, including14 symbols within each 1 ms subframe.

In the example of FIG. 4, a low latency or burst mode frame 420 mayreplace a number of the downlink subframes 425 with burst subframes 440.Burst subframes 440, similarly as discussed above, may be transmitted ina different hierarchical layer than downlink subframes 425, specialsubframes 430, and uplink subframes 435. Burst subframes 440, inexamples, may include 88 symbols, and may include downlink symbols 445,special symbols 450, and uplink symbols 455. Each of the symbols 445,450, and 455 may have a reduced symbol duration relative to the legacysymbols (e.g., symbols 266 of FIG. 2), such as described above withrespect to FIG. 3A. Such reduced symbol duration may enableacknowledgment of transmissions with a reduced latency relative toacknowledgment of transmissions according to legacy HARQ schemes.

For example, in legacy TDD frame 410, a UE may receive a downlinktransmission in downlink subframe 425 and transmit an acknowledgmentrelated to the downlink transmission according to a legacy HARQ schemein which ACK/NACK it transmitted in a first available subframe at orafter k+4 subframes from the receipt of the downlink transmission. Inthe example of FIG. 4, subframe k+4 from downlink subframe 425 isanother downlink subframe, and the ACK/NACK 460 is thus transmitted infollowing uplink subframe 465. Thus, in this example, there is a 7 msdelay between downlink subframe 425 and providing the ACK/NACK 460associated with the subframe. In the event that a retransmission isnecessary based on the ACK/NACK 460, the retransmission may then bescheduled for a subsequent downlink subframe, resulting in a RTT that,in this example, would be a minimum of 11 ms. In the event that anacknowledgment may be provided in the fourth subframe following adownlink transmission (e.g., in FDD mode ACK/NACK may be consistentlytransmitted in subframe k+4), a minimum RTT may then be 8 ms.

Within burst subframes 440, in the example of FIG. 4, the latencyrelated to providing acknowledgment of a transmission may be reduced.For example, transmissions using the second hierarchical layer mayfollow similar HARQ techniques as with legacy transmissions, and anacknowledgment of a transmission may be provided in a symbol that is k+4symbols after receipt of a transmission, or in a first available symbolfor transmission afterward. For example, a UE may receive downlinktransmission in symbol 445 and provide an ACK/NACK 470 in uplink symbol455, which is five symbols after the receipt of downlink transmission indownlink symbol 445 because the fourth symbol following the transmissionis a special symbol 450. Thus, the UE may provide ACK/NACK 470 of thedownlink transmission within the burst subframe 440, which is less thanone ms following the receipt of the downlink transmission in downlinksymbol 445. In some examples, similarly as discussed above with respectto FIG. 3A, the symbol duration for symbols in the burst subframe 440may be 11.36 μs, resulting in an acknowledgment being provided in thisexample 56.8 μs following the downlink symbol 445 transmission. The eNBmay then schedule any required retransmission and thus may provide, insome examples, a resulting RTT of approximately 100 μs or less.

While ACK/NACK 470 is described with respect to a UE receiving adownlink symbol 445, similar functions may be performed for uplinktransmissions. For example, a UE may transmit an uplink symbol 480 to aneNB, which may be acknowledged by the eNB through ACK/NACK 475 that isprovided in downlink symbol 485. In the even that a retransmission isnecessary, such a retransmission may be provided in a subsequent uplinksymbol from the UE and thus may again provide, in some examples, aresulting RTT of approximately 100 μs or less. Accordingly, latencyassociated with transmissions in burst subframes 440 may besignificantly reduced. Such reduced latency may enable enhanced datarates, through reduced RTTs which may reduce overall retransmissiontimes. Such reduced RTTs may thus impact the time that it may take toachieve the TCP segment error rate, and may thus enhance the overalldata rate that is achievable between a UE and an eNB.

While the examples discussed with reference to FIGS. 3A, 3B, and 4describe first hierarchical layer TDD transmissions, such techniques arealso applicable to other transmission modes. FIG. 5 is a block diagram500 conceptually illustrating another example of radio frames anddifferent subframes that may be transmitted on different layers of awireless communication system, in accordance with an aspect of thepresent disclosure. The radio frames of FIG. 5 may be transmitted usingportions of the wireless communications system 100 described withreference to FIG. 1 between one or more access points 105 and one ormore UEs 115, for example. In this example, similarly as described withrespect to FIG. 3A, a legacy FDD frame 510 may include ten 1 ms downlinksubframes 525. The downlink subframes 525 may include a subframestructure as discussed above with respect to FIGS. 2 and 3, including 14symbols within each 1 ms subframe.

In the example of FIG. 5, a low latency or burst mode frame 520 mayreplace a number of the downlink subframes 525 with burst subframes 540.Burst subframes 540, similarly as discussed above, may be transmitted ina different hierarchical layer than downlink subframes 525. In someexamples, however, FDD downlink subframes 525 may include schedulinginformation in the first two symbols of the subframe 525. In order toprovide compatibility with UEs that are not capable of operating in thesecond hierarchical layer, burst subframes 540, in examples, may includetwo legacy FDD OFDM downlink symbols 545 and 550, followed by 76 TDDburst mode symbols 555, which may include downlink symbols, specialsymbols, and uplink symbols similarly as discussed above with respect toFIGS. 3A, 3B, and 4. The legacy FDD OFDM symbols 545 and 550 may bereceived by a UE that is not capable of receiving burst mode symbols555, and may perform legacy scheduling functions based on theinformation in legacy FDD symbols 545 and 550. In some examples, burstsubframes 540 may be selected to correspond to FDD subframes 525 thatmay provide multicast or broadcast content, and that legacy UEs may notbe configured to receive, and therefore such legacy UEs in such caseswould ignore the remainder of such subframes in any event.

Thus, in the example, of FIG. 5, hybrid multiplexing may be implemented,in which a first hierarchical layer may operate using FDD, while asecond hierarchical layer may operate using TDD. According to variousexamples, the first hierarchical layer may operate in FDD, TDD, orsupplemental downlink (SDL) mode, and the second hierarchical layer mayoperate in FDD, TDD, or SDL mode independently of the mode of the firsthierarchical layer. Similarly as discussed above, the burst mode symbols555 may have a reduced symbol duration relative to the legacy symbols(e.g., symbols 266, 366 of FIG. 2 or 3). Such reduced symbol durationmay enable acknowledgment of transmissions with a reduced latencyrelative to acknowledgment of transmissions according to legacy HARQschemes.

While the example discussed with reference to FIG. 5 describes TDDoperation in a second hierarchical layer, other modes, such as FDD orSDL, may be used in the second hierarchical layer, as discussed withreference to FIG. 3B, for instance. FIG. 6 is a block diagram 600conceptually illustrating another example of radio frames and differentsubframes that may be transmitted on different layers of a wirelesscommunication system, in accordance with an aspect of the presentdisclosure. The radio frames of FIG. 6 may be transmitted using portionsof the wireless communications system 100 described with reference toFIG. 1 between one or more access points 105 and one or more UEs 115,for example. In this example, similarly as described with respect toFIG. 5, a legacy FDD frame 610 may include ten 1 ms downlink subframes625. The downlink subframes 625 may include a subframe structure asdiscussed above with respect to FIGS. 2-5, including 14 symbols withineach 1 ms subframe.

In the example of FIG. 6, a low latency or burst mode frame 620 mayreplace a number of the downlink subframes 625 with burst subframes 640.Burst subframes 640, similarly as discussed above, may be transmitted ina different hierarchical layer than downlink subframes 625. In someexamples, similarly as discussed above with respect to FIG. 5, FDDdownlink subframes 625 may include scheduling information in the firsttwo symbols of the subframe 625. In order to provide compatibility withUEs that are not capable of operating in the second hierarchical layer,burst subframes 640, in examples, may include two legacy FDD OFDMsymbols 645 and 650, followed by 76 SDL burst mode downlink symbols 655.The legacy FDD OFDM symbols 645 and 650 may be received by a UE that isnot capable of receiving burst mode symbols 655, and may perform legacyscheduling functions based on the information in legacy FDD OFDM symbols645 and 650. In some examples, burst subframes 640 may be selected tocorrespond to FDD subframes 625 that may provide multicast or broadcastcontent, and that legacy UEs may not be configured to receive, andtherefore such legacy UEs in such cases would ignore the remainder ofsuch subframes in any event. Similarly as discussed above, the burstmode symbols 655 may have a reduced symbol duration relative to thelegacy symbols (e.g., symbols 266, 366 of FIG. 2 or 3). Such reducedsymbol duration may enable acknowledgment of transmissions with areduced latency relative to acknowledgment of transmissions according tolegacy HARQ schemes.

While various of the above examples provide different hierarchicallayers of communication using one component carrier, techniquesdescribed herein are applicable to wireless communications systems thatmay utilize carrier aggregation. FIG. 7 is a block diagram conceptuallyillustrating a wireless communications system that may utilize carrieraggregation, in accordance with aspects of the present disclosure. Inthis example, a portion of a wireless communications system 700 isillustrated in which eNB 105-c may communicate with UE 115-c usingcarrier aggregation. The wireless communications system 700 may be anexample of portions of the wireless communications system 100 describedwith reference to FIG. 1. Moreover, the eNB 105-c may be an example ofone of the access points 105 of FIG. 1, while the UEs 115-c may beexamples of the UEs 115 described with reference to FIG. 1. In someexamples, eNB 105-c and UE 115-c may be configured to operate onmultiple hierarchical layers, similarly as discussed above with respectto FIGS. 1-6.

The system 700 can include a user equipment 115-c, which can communicatewith eNB 105-c using one or more component carriers 1 through N(CC₁-CC_(N)). While only one user equipment 115-c and one eNB 105-c areillustrated in FIG. 7, it will be appreciated that the system 700 caninclude any number of UEs 115 and/or eNBs 105. The eNB 105-c cantransmit information to the user equipment 115-c over forward (downlink)channels 732 through 742 on component carriers CC₁ through CC_(N). Inaddition, the user equipment 115-c can transmit information to the eNB105-c over reverse (uplink) channels 734 through 744 on componentcarriers CC₁ though CC_(N).

In legacy LTE-A based systems, the UE 115-c may be configured withmultiple component carriers utilized by the eNB 105-c to enable a wideroverall transmission bandwidth. As illustrated in FIG. 7, the userequipment 115-c can be configured with “component carrier 1” 730 through“component carrier N” 740, where N is an integer greater than or equalto one. While FIG. 7 depicts two component carriers, it is to beappreciated that the user equipment 115-c can be configured with anysuitable number of component carriers and, accordingly, the subjectmatter disclosed herein and the claims are not limited to two componentcarriers. Component carrier 730 through 740 can include respectivedownlink channels 732 through 742 as well as respective uplink channels734 through 744.

In multi-carrier operations, each component carrier 730 through 740 mayoperate using a specified bandwidth. For example, the bandwidth for eachcomponent carrier 730 through 740 may be 20 MHz. In some examples, UE115-c and eNB 105-c may be configured to operate in a secondhierarchical layer in which the bandwidth for transmitting may be scaledaccording to the aggregated bandwidth of the component carriers. In someexamples, UE 115-a and eNB 105-c may transmit time division multiplexedsubframes, in a similar manner as discussed above, on a firsthierarchical layer and a second hierarchical layer. In examples, one ormore subframes transmitted on the first hierarchical layer may beconcurrently transmitted using two or more separate component carriers730-740. One or more burst subframes of the second hierarchical layermay be multiplexed with the subframes transmitted on the firsthierarchical layer, with the burst subframes transmitted using onecarrier having a bandwidth that is greater than the bandwidth of thecomponent carriers 730-740. For example, if two component carriers areused for first hierarchical layer transmissions each having 20 MHzbandwidth, the burst subframe may be transmitted using a 40 MHzbandwidth. Thus, the radio frequency spectrum occupied by the twocomponent carriers would overlap with the radio frequency spectrumoccupied by the burst subframe. However, the two component carriers mayhave associated guard bands that may not be required for the burstsubframe transmission, and thus the bandwidth may be used moreefficiently.

With reference now to FIG. 8A is a block diagram 800-a conceptuallyillustrating an example of radio frames and different subframes that maybe transmitted on different component carriers and on different layersof a wireless communication system, in accordance with an aspect of thepresent disclosure. The radio frames of FIG. 8A may be transmitted usingportions of the wireless communications systems 100 and/or 700 describedwith reference to FIGS. 1 and/or 7 between one or more access points oreNBs 105 and one or more UEs 115, for example. In this example, four TDDradio frames 805 through 820 may be concurrently transmitted usingcarrier aggregation. Each of the TDD frames 805-820 may include ten 1 mssubframes that include downlink subframes 825, special subframes 830,and uplink subframes 835. Time division multiplexed with the subframes825, 830, 835, according to examples, are burst subframes 840. Thedownlink subframes 825, special subframes 830, and uplink subframes 835may include a subframe structure as discussed above with respect to FIG.2, including 14 symbols within each 1 ms subframe.

In the example of FIG. 8A, low latency burst subframes 840 may betransmitted in a different hierarchical layer than downlink subframes825, special subframes 830, and uplink subframes 835. Burst subframes840, in examples, may include 88 symbols that are each scaled inbandwidth to occupy the aggregated bandwidth of each of the componentcarriers used to transmit the legacy subframes 825, 830, and 835. In theexample of FIG. 8A, burst subframes 840 may be TDD burst subframes andmay include downlink symbols 845, special symbols 850, and uplinksymbols 855. Each of the symbols 845, 850, and 855 may have a reducedsymbol duration relative to the legacy symbols (e.g., symbols 266, 366of FIGS. 2, 3), and in some examples have a symbol duration of 11.36 μsper symbol, including a useful symbol duration of 8.33 μs and a cyclicprefix duration of 8.03 μs. Symbols 845, 850, and 855 may have increasedtone spacing for subcarriers relative to legacy symbols, and in someexamples have a tone spacing of 120 kHz. In some examples, a hybrid UE,second layer UE, and/or eNB may generate legacy symbols such as symbolsfor subframes 825, 830, and 835 utilizing an internal clock configuredto generate legacy symbols having a first symbol duration, and maygenerate the symbols 845, 850, 855 of burst subframe by adapting theclock to generate symbols 845, 850, 855 having a second symbol duration.Hybrid UEs, second layer UEs, and/or eNBs may scale the bandwidth usedfor transmission of the burst subframes 840 through adapting an RFtransmit/receive chain to transmit using the scaled bandwidth.

In some examples, hybrid UEs (e.g., UE 115-a of FIG. 1) may beconfigured to communicate using both legacy subframes 825, 830, 835through carrier aggregation, and burst subframes 840 using scaledbandwidth. Likewise, second layer UEs (e.g., UE 115-b of FIG. 1) may beconfigured to communicate using only burst subframes 840 using scaledbandwidth, and legacy UEs may be configured to communicate using onlylegacy subframes 825, 830, 835 through carrier aggregation. In exampleswhere a UE may communicate on just one hierarchical layer, subframes ofthe other hierarchical layer(s) may be ignored.

FIG. 8B is a block diagram 800-b conceptually illustrating an example ofradio frames and different subframes that may be transmitted ondifferent component carriers and on different layers of a wirelesscommunication system, in accordance with an aspect of the presentdisclosure. The radio frames of FIG. 8B may be transmitted usingportions of the wireless communications system 100 and/or 700 describedwith reference to FIGS. 1 and/or 7 between one or more access points oreNBs 105 and one or more UEs 115, for example. FIG. 8B may include TDDradio frames 805-a, 810-a, 815-a, 820-a, downlink subframes 825-a,special subframes 830-a, uplink subframes 835-a, burst subframes 840-a,downlink symbols 845-a, special symbols 850-a, and uplink symbols 855-awhich may be similar to, or the same as, TDD radio frames 805, 810, 815,820, downlink subframes 825, special subframes 830, uplink subframes835, burst subframes 840, downlink symbols 845, special symbols 850, anduplink symbols 855 described above with reference to FIG. 8A. Asdepicted in the example of FIG. 8B, hybrid and second layer UEs (e.g.,UE 115-b of FIG. 1) may be configured to communicate on burst subframes840-a using scaled bandwidth on a subset set of the aggregated componentcarriers.

While the examples discussed with reference to FIG. 8A describes firsthierarchical layer TDD transmissions, such techniques are alsoapplicable to other transmission modes. FIG. 9 is a block diagram 900conceptually illustrating another example of radio frames and differentsubframes that may be transmitted on different layers of a wirelesscommunication system, in accordance with an aspect of the presentdisclosure. The radio frames of FIG. 9 may be transmitted using portionsof the wireless communications systems 100 and/or 700 described withreference to FIGS. 1 and/or 7 between one or more access points 105 andone or more UEs 115, for example. In this example, similarly asdescribed with respect to FIG. 8A, FDD radio frames 905 through 920 maybe concurrently transmitted using carrier aggregation. Each of the FDDframes 905-920 may include ten 1 ms subframes that include downlinksubframes 925. Time division multiplexed with the subframes 925,according to examples, are burst subframes 940. The downlink subframes925 may include a subframe structure as discussed above with respect toFIG. 2, including 14 symbols within each 1 ms subframe.

In the example of FIG. 9, a number of the downlink subframes 925 may bereplaced with burst subframes 940. Burst subframes 940, similarly asdiscussed above, may be transmitted in a different hierarchical layerthan downlink subframes 925. In some examples, however, FDD downlinksubframes 925 may include scheduling information in the first twosymbols of the subframe 925. In order to provide compatibility with UEsthat are not capable of operating in the second hierarchical layer,burst subframes 940, in examples, may include two legacy FDD OFDMsymbols 945 and 950 transmitted according to legacy carrier aggregationtechniques, followed by 76 TDD burst mode symbols having scaledbandwidth.

The burst OFDM symbols may include downlink symbols, special symbols,and uplink symbols similarly as discussed above with respect to FIGS.3A-5. The legacy FDD OFDM symbols 945 and 950 may be received by a UEthat is not capable of receiving burst mode symbols 955, and may performlegacy scheduling functions based on the information in legacy FDD OFDMsymbols 945 and 950. Similarly as discussed above, the burst modesymbols 955 may have a reduced symbol duration relative to the legacysymbols (e.g., symbols 266, 366 of FIG. 2 or 3). Such reduced symbolduration may enable acknowledgment of transmissions with a reducedlatency relative to acknowledgment of transmissions according to legacyHARQ schemes, and may enable higher data rates. While the example ofFIGS. 8A, 8B, and 9 describe TDD burst subframes 840 and 940, FDD and/orSDL burst subframes may also be transmitted, similarly as discussedabove.

With reference now to FIG. 10 a block diagram 1000 conceptuallyillustrating another example of radio frames and different subframesthat may be transmitted on different layers of a wireless communicationsystem is described, in accordance with an aspect of the presentdisclosure. The radio frames of FIG. 10 may be transmitted usingportions of the wireless communications systems 100 and/or 700 describedwith reference to FIGS. 1 and/or 7 between one or more access points 105and one or more UEs 115, for example. In this example, similarly asdescribed with respect to FIG. 9, FDD radio frames 1005 through 1020 maybe concurrently transmitted using carrier aggregation. Each of the FDDframes 1005-1020 may include ten 1 ms subframes that include downlinksubframes 1025. Time division multiplexed with the subframes 1025,according to examples, are burst subframes 1040. The downlink subframes1025 may include a subframe structure as discussed above with respect toFIG. 2, including 14 symbols within each 1 ms subframe.

In the example of FIG. 10, a number of the downlink subframes 1025 maybe replaced with burst subframes 1040. Burst subframes 1040, similarlyas discussed above, may be transmitted in a different hierarchical layerthan downlink subframes 1025. In some examples, however, FDD downlinksubframes 1025 may include scheduling information in the first twosymbols of the subframe 1025. In order to provide compatibility with UEsthat are not capable of operating in the second hierarchical layer,burst subframes 1040, in examples, may include two legacy FDD OFDMsymbols 1045 and 1050 transmitted according to legacy carrieraggregation techniques, followed by 12 FDD scaled bandwidth OFDM symbols1055.

In such examples, each of the 12 FDD scaled bandwidth symbols may havethe same symbol duration as legacy signals, but may be transmitted usingscaled bandwidth to provide one carrier with increased bandwidth ratherthan four separate carriers. Similarly as discussed above, the scaledbandwidth symbols may have enhanced efficiencies as a result of, forexample, eliminating guard bands associated with the four separatecarriers. The legacy FDD symbols 1045 and 1050 may be received by a UEthat is not capable of receiving burst mode symbols 1055, and mayperform legacy scheduling functions based on the information in legacyFDD symbols 1045 and 1050. While the example of FIG. 10 illustrates FDDburst subframes 1040, TDD and/or SDL burst subframes may also betransmitted in a similar manner.

FIGS. 11A and 11B are block diagrams conceptually illustrating devices,such as eNBs or UEs, for use in wireless communications in accordancewith aspects of the present disclosure. With reference first to FIG.11A, a block diagram 1100 illustrates a device 1105 for use in wirelesscommunications in accordance with various examples. In some examples,the device 1105 may be an example of one or more aspects of the accesspoints, or eNBs 105 and/or UEs 115 described with reference to FIGS. 1and/or 7. The device 1105 may also be a processor. The device 1105 mayinclude a receiver module 1110, a layer configuration module, and/or atransmitter module 1130. Each of these components may be incommunication with each other.

The components of the device 1105 may, individually or collectively, beimplemented with one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other examples, other types of integrated circuits may be used (e.g.,Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), andother Semi-Custom ICs), which may be programmed in any manner known inthe art. The functions of each unit may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some examples, the receiver module 1110 may be or include a radiofrequency (RF) receiver, such as an RF receiver operable to receivetransmissions on two or more hierarchical layers (e.g., through legacyLTE subframes and burst subframes). The receiver module 1110 may be usedto receive various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunications system, such as one or more communication links 125 ofthe wireless communications system 100 described with reference to FIG.1.

In some examples, the transmitter module 1130 may be or include an RFtransmitter, such as an RF transmitter operable to transmit on two ormore hierarchical layers (e.g., through legacy LTE subframes and burstsubframes). The transmitter module 1130 may be used to transmit varioustypes of data and/or control signals (i.e., transmissions) over one ormore communication links of a wireless communications system, such asone or more communication links 125 of the wireless communicationssystem 100 described with reference to FIG. 1.

In some examples, the layer configuration module 1120 may configureand/or perform layer configuration for device 1105 operation in awireless communications system having two or more hierarchical layers.Layer configuration module 1120 may, for example configure device 1105to operate within the wireless communications system having firsthierarchical layer transmissions with a first subframe type having afirst RTT. Layer configuration module 1120 may also perform operationsat a second hierarchical layer multiplexed with the first hierarchicallayer, the second hierarchical layer having second layer transmissionswith a second subframe type having a second RTT that is less than thefirst RTT. In some examples, the layer configuration module mayconfigure or identify several regions of a carrier with different symboldurations. Configuration and operation may include transmission and/orreception of legacy and/or burst subframes, and may include transmissionand/or reception of symbols of different durations TDM or FDM, such asdescribed above with respect to FIGS. 1-10, for example.

Referring now to FIG. 11B, a block diagram 1150 illustrates a device1155 for use in wireless communications, in accordance with variousaspects of the present disclosure. In some examples, the device 1155 maybe an example of one or more aspects of the access points or eNBs 105,UEs 115, and/or device 1105 described with reference to FIGS. 1, 7,and/or 11A. The device 1155 may also be a processor. The device 1155 mayinclude a receiver module 1110, a layer configuration module 1160,and/or a transmitter module 1130. Each of these components may be incommunication with each other.

The components of the device 1155 may, individually or collectively, beimplemented with one or more ASICs adapted to perform some or all of theapplicable functions in hardware. Alternatively, the functions may beperformed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1110-a may be an example of thereceiver module 1110 of FIG. 11A. The receiver module 1110-a may be orinclude a radio frequency (RF) receiver, such as an RF receiver operableto receive transmissions on two or more hierarchical layers (e.g.,through legacy LTE subframes and burst subframes). The RF receiver, insome examples, may include separate receivers for the first and secondhierarchical layers. In other examples, the RF receiver may include asingle receiver, or a single receiver per transmit/receive chain, and aclock module 1180 of layer configuration module 1160 may be adapted toprocess received symbols having different symbol durations. The receivermodule 1110-a may be used to receive various types of data and/orcontrol signals (i.e., transmissions) over one or more communicationlinks of a wireless communications system including over two or morehierarchical layers, such as one or more communication links 125 of thewireless communications system 100 described with reference to FIG. 1.

In some examples, the transmitter module 1130-a may be an example of thetransmitter module 1130 of FIG. 11A. The transmitter module 1130-a maybe or include a radio frequency (RF) transmitter, such as an RFtransmitter operable to transmit on two or more hierarchical layers(e.g., through legacy LTE subframes and burst subframes). The RFtransmitter 1130-a, in some examples, may include separate transmittersfor the first and second hierarchical layers. In other examples, the RFtransmitter may include a single transmitter, or a single transmitterper transmit/receive chain, and a clock module 1180 of layerconfiguration module 1160 may be adapted to generate symbols havingdifferent symbol durations. The transmitter module 1130-a may be used toreceive various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunications system including over two or more hierarchical layers,such as one or more communication links 125 of the wirelesscommunications system 100 described with reference to FIG. 1.

The layer configuration module 1160 may be an example of the layerconfiguration module 1120 described with reference to FIG. 11A and mayinclude a first layer configuration module 1170, a burst mode module1175, clock module 1180, and optional scalable bandwidth module 1185.Each of these components may be in communication with each other.

In some examples, the first layer configuration module 1170 may performconfiguration for the device 1155 to operate in the first hierarchicallayer and perform at least some functions for device operation in thefirst hierarchical layer, such as described above with respect to FIGS.1-10, for example. In some examples, the first layer configurationmodule 1170, in conjunction with the transmitter module 1130-a or thereceiver module 1110-a, may communicate (e.g., transmit or receive) asignal in a symbol of one region, where the signal is indicative of asymbol duration of another region. The burst mode module 1175 mayconfigure for the device 1155 to operate in the second hierarchicallayer and perform at least some functions for device operation in thesecond hierarchical layer, such as described above with respect to FIGS.1-10, for example. The clock module 1180 may perform clock adaptation toallow a clock to be adapted in order to enable generation of symbols,and processing of received symbols, having different symbol durations,such as described above with respect to FIGS. 1-10, for example. In someexamples, the clock module 1180 may adjust or identify a time durationor periodicity of a carrier region configured with a particular symbolduration. Scalable bandwidth module 1185 may perform bandwidth scalingin examples that may utilize carrier aggregation to transmit/receivemultiple component carriers for legacy subframes and utilize scaledbandwidth on a single component carrier for burst subframes, such asdescribed above with respect to FIGS. 1 and 7-10, for example.Additionally or alternatively, scalable bandwidth module 1185 may adjustor identify (e.g., based on a latency requirement) bandwidth of acarrier region configured with a particular symbol duration. In someexamples, the region configuration module 1190 may configure or identifyone or several regions of a carrier with different symbol durations,where the various regions may be TDM or FDM. The region configurationmodule 1190, in conjunction with the first layer configuration module1170, may configure or identify a guard band between regions havingdifferent symbol durations.

FIG. 12 is a block diagram conceptually illustrating a design of an eNB,in accordance with aspects of the present disclosure, configured forhierarchical communications within a wireless communications system. Inexamples, the eNB 105-d may be an example of one or more aspects of theaccess points, eNBs, or devices 105, 1105, and/or 1155 described withreference to FIGS. 1, 7 and/or 11. The eNB 105-d may be configured toimplement at least some of the hierarchical communications features andfunctions described with respect to FIGS. 1-10. The eNB 105-d mayinclude a processor module 1210, a memory module 1220, at least onetransceiver module (represented by transceiver module(s) 1255), at leastone antenna (represented by antenna(s) 1260), and/or an eNB LTE layerconfiguration module 1270. The eNB 105-d may also include one or both ofan eNB communications module 1230 and a network communications module1240. Each of these components may be in communication with each other,directly or indirectly, over one or more buses 1235.

The memory module 1220 may include random access memory (RAM) and/orread-only memory (ROM). The memory module 1220 may storecomputer-readable, computer-executable software (SW) code 1225containing instructions that are configured to, when executed, cause theprocessor module 1210 to perform various functions described herein forhierarchical communications in two or more layers, including thetransmission and/or reception of burst subframes having relatively lowlatency, such as described above. In some examples, the SW code 1225 mayinclude instructions that are configured to cause the processor module1210 to configured a carrier with a first region having a first symbolduration and a second region having a second symbol duration, where thefirst and second symbol durations are different—e.g., the first symbolduration may be longer than the second symbol duration. Alternatively,the software code 1225 may not be directly executable by the processormodule 1210 but be configured to cause the eNB 105-d, e.g., whencompiled and executed, to perform various of the functions describedherein.

The processor module 1210 may include an intelligent hardware device,e.g., a central processing unit (CPU), a microcontroller, an ASIC, etc.The processor module 1210 may process information received through thetransceiver module(s) 1255, the base station communications module 1230,and/or the network communications module 1240. The processor module 1210may also process information to be sent to the transceiver module(s)1255 for transmission through the antenna(s) 1260, to the eNBcommunications module 1230 for transmission to one or more other basestations or eNBs 105-n and 105-m, and/or to the network communicationsmodule 1240 for transmission to a core network 130-a, which may be anexample of aspects of the core network 130 described with reference toFIG. 1. The processor module 1210 may handle, alone or in connectionwith the eNB layer configuration module 1270, various aspects ofhierarchical communications in two or more hierarchical layers, such asdescribed above with respect to FIGS. 1-10.

The transceiver module(s) 1255 may include a modem configured tomodulate the packets and provide the modulated packets to the antenna(s)1260 for transmission, and to demodulate packets received from theantenna(s) 1260. The transceiver module(s) 1255 may be implemented asone or more transmitter modules and one or more separate receivermodules. The transceiver module(s) 1255 may support communications intwo or more hierarchical layers (e.g., through legacy LTE subframes andburst subframes), or may support communications with regions ofdifferent symbol durations that are TDM or FDM. The transceivermodule(s) 1255 may be configured to communicate bi-directionally, viathe antenna(s) 1260, with one or more of the UEs or devices 115, 1105and/or 1155 described with reference to FIGS. 1, 7 and/or 11, forexample. The eNB 105-d may include multiple antennas 1260 (e.g., anantenna array). The eNB 105-d may communicate with the core network130-a through the network communications module 1240. The eNB 105-d maycommunicate with other access points or eNBs, such as the eNB 105-nand/or 105-m, using the eNB communications module 1230.

According to the architecture of FIG. 12, the eNB 105-d may furtherinclude a communications management module 1250. The communicationsmanagement module 1250 may manage communications with other basestations, eNBs, and/or devices. The communications management module1250 may be in communication with some or all of the other components ofthe eNB 105-d via the bus or buses 1235. Alternatively, functionality ofthe communications management module 1250 may be implemented as acomponent of the transceiver module(s) 1255, as a computer programproduct, and/or as one or more controller elements of the processormodule 1210.

The eNB layer configuration module 1270 may be configured to performand/or control some or all of the eNB hierarchical communicationsfunctions or aspects described with reference to FIGS. 1-10. Forexample, the eNB layer configuration module 1270 may be configured tosupport communications on one or more hierarchical layers of a wirelesscommunications system having multiple hierarchical layers, such asthrough transmission/reception of burst subframes; and the eNB layerconfiguration module 1270 may be configured to support a wirelesscommunications system in which several regions of a carrier havingdifferent symbol duration coexist The eNB layer configuration module1270 may include an eNB first layer configuration module 1280 toconfigure the eNB 105-d for communications in a wireless communicationsystem having multiple hierarchical layers or to signal, in a symbol ofone region, a symbol duration of another region, an eNB burst modemodule 1285 configured to perform functions related to the transmissionand reception of burst subframes, eNB clock module 1290 configured toprovide clock adaptation or to adjust a time duration or periodicity ofa carrier region based on symbol duration, eNB scalable bandwidth module1295 configured to perform bandwidth scaling across multiple subcarriersor to adjust bandwidth of a carrier region configured with a particularsymbol duration, and eNB region configuration module 1297 to configuredone or several regions of a carrier with different symbol durations orguard bands. The eNB layer configuration module 1270 may be an exampleof similar modules (e.g., modules 1120 and 1160) described withreference to FIGS. 11A and/or 11B. The eNB layer configuration module1270, or portions of it, may include a processor and/or some or all ofthe functionality of the eNB layer configuration module 1270 may beperformed by the processor module 1210 and/or in connection with theprocessor module 1210.

FIG. 13 is a block diagram 1300 conceptually illustrating a design of aUE, in accordance with aspects of the present disclosure, configured forhierarchical communications in a wireless communications system. The UE115-d may have various other configurations and may be included or bepart of a personal computer (e.g., laptop computer, netbook computer,tablet computer, etc.), a cellular telephone, a PDA, a digital videorecorder (DVR), an internet appliance, a gaming console, an e-readers,etc. The UE 115-d may have an internal power supply (not shown), such asa small battery, to facilitate mobile operation. In some examples, theUE 115-d may be an example of one or more of the UEs or devices 115,1105 and/or 1155 described with reference to FIGS. 1, 7, 11A and/or 11B.The UE 115-d may be configured to communicate with one or more of theaccess points, eNBs or devices 105, 1105 and/or 1155 described withreference to FIGS. 1, 7, 11A, 11B and/or 12.

The UE 115-d may include a processor module 1310, a memory module 1320,at least one transceiver module (represented by transceiver module(s)1370), at least one antenna (represented by antenna(s) 1380), and/or aUE layer configuration module 1340. Each of these components may be incommunication with each other, directly or indirectly, over one or morebuses 1335.

The memory module 1320 may include RAM and/or ROM. The memory module1320 may store computer-readable, computer-executable software (SW) code1325 containing instructions that are configured to, when executed,cause the processor module 1310 to perform various functions describedherein for hierarchical communications or communications with regions ofdifferent symbol durations in a wireless communication system.Alternatively, the software code 1325 may not be directly executable bythe processor module 1310 but be configured to cause the UE 115-d (e.g.,when compiled and executed) to perform various of the UE functionsdescribed herein.

The processor module 1310 may include an intelligent hardware device,e.g., a CPU, a microcontroller, an ASIC, etc. The processor module 1310may process information received through the transceiver module(s) 1370and/or information to be sent to the transceiver module(s) 1370 fortransmission through the antenna(s) 1380. The processor module 1310 mayhandle, alone or in connection with the UE layer configuration module1340, various aspects of hierarchical communications on one or morehierarchical layers of a wireless communications system, includingtransmission and reception of burst subframes, for example; and theprocessor module 1310, e.g., in conjunction with the UE layerconfiguration module 1340, may identify and communicate with one orseveral regions of a carrier having different symbol durations.

The transceiver module(s) 1370 may be configured to communicatebi-directionally with eNBs. The transceiver module(s) 1370 may beimplemented as one or more transmitter modules and one or more separatereceiver modules. The transceiver module(s) 1370 may supportcommunications on at least one layer of a multiple hierarchical layerwireless communications system. The transceiver module(s) 1370 mayinclude a modem configured to modulate the packets and provide themodulated packets to the antenna(s) 1380 for transmission, and todemodulate packets received from the antenna(s) 1380. While the UE 115-dmay include a single antenna, there may be examples in which the UE115-d may include multiple antennas 1380.

According to the architecture of FIG. 13, the UE 115-d may furtherinclude a communications management module 1330. The communicationsmanagement module 1330 may manage communications with various basestations or eNBs. The communications management module 1330 may be acomponent of the UE 115-d in communication with some or all of the othercomponents of the UE 115-d over the one or more buses 1335.Alternatively, functionality of the communications management module1330 may be implemented as a component of the transceiver module(s)1370, as a computer program product, and/or as one or more controllerelements of the processor module 1310.

The UE layer configuration module 1340 may be configured to performand/or control some or all of the UE hierarchical communicationsfunctions or aspects, or communications with regions of different symboldurations that are TDM or FDM, described in FIGS. 1-10 related to usingcommunication on one or more hierarchical layers in a wirelesscommunications system having multiple hierarchical layers. For example,the UE layer configuration module 1340 may be configured to processreceived symbols and/or generate symbols that may be included in one ormore burst subframes. The UE layer configuration module 1340 may includea UE first layer configuration module 1350 to configure the UE 115-d tooperate in the wireless communications system with multiple hierarchicallayers or having regions configured with different symbol durations, aUE burst mode module 1355 configured to handle processing of receivedsymbols from one or more burst subframes and/or generation of burst modesymbols, UE clock module 1360 configured to provide clock adaptationbased on symbol duration or to identify a time duration or periodicityof a carrier region having a particular symbol duration, UE scalablebandwidth module 1365 configured to perform bandwidth scaling acrossmultiple subcarriers or to identify bandwidth of a carrier regionconfigured with a particular symbol duration, and UE regionconfiguration module 1367 to identify one or several regions of acarrier configured with different symbol durations. The UE layerconfiguration module 1340, or portions of it, may include a processorand/or some or all of the functionality of the UE layer configurationmodule 1340 may be performed by the processor module 1310 and/or inconnection with the processor module 1310.

FIG. 14 is a block diagram 1400 conceptually illustrating a design oftransceiver module 1405, in accordance with aspects of the presentdisclosure. The transceiver module 1405 may have various otherconfigurations and may be included or be part of a UE or device such asUEs or devices 115, 1105, and/or 1155 of FIGS. 1, 7, 11A, 11B, and/or13. Transceiver module 1405 may also be included or be a part of anaccess point or eNB, such as access points or eNBs 105 of FIGS. 1, 7,and/or 12. The transceiver module 1405 may be an example of thetransceiver module(s) 1255 and/or 1370 of FIGS. 12 and/or 13. Thetransceiver module 1405 may include multiple receive chains 1410,including receive chain 0 1410-0 through receive chain n 1410-n, andmultiple transmit chains 1415, including transmit chain 0 1410-0 throughtransmit chain n 1410-n. Each of receive chains 1410-0-1410-n andtransmit chains 1415-0-1415-n may be coupled with an associated antenna1412, namely antenna 0 1412-0 through antenna n 1412-n, respectively.Receive chains 1410-0-1410-n may, respectively, include RF modules1420-0 through 1420-n, analog-to-digital converter (ADC) modules 1425-athrough 1425-n, and fast Fourier transform (FFT) module 1430-0 through1430-n, and may be coupled with a demodulator 1435. Transmit chains1415-0-1415-n may include, respectively, RF modules 1450-0 through1450-n, digital-to-analog converter (DAC) modules 1455-0 through 1455-n,and inverse FFT (IFFT) modules 1460-0 through 1460-n, and may be coupledwith a modulator 1440.

According to some examples, transceiver module 1405 may be configured tooperate in different hierarchical layers in a wireless communicationssystem, and components of the transmit and receive chains may beconfigured and adapted to transmit and receive symbols having differentsymbol durations based on whether the symbols are transmitted as part ofa burst subframe or as part of a legacy subframe. In some examples,clock module 1470 may be adapted to clock components at different ratesin order to generate symbols having different symbol durations, orreceive and process symbols having different symbol durations.

In examples that may utilize hierarchical layers with scalablebandwidth, transmit and receive chains may be adapted totransmit/receive carriers having different bandwidths based on whether acarrier is one of multiple component carriers, or a single carrierhaving a bandwidth that is greater than the bandwidth of a legacycomponent carrier. In some examples, multiple transmit and/or receivechains may be used to transmit component carriers in a carrieraggregation transmission of legacy subframes. In the event that one ormore burst subframes are to be transmitted/received, one or more of thetransmit and/or receive chains may be disabled with one of the transmitand/or receive chains remaining enabled to transmit/receive the signalcomponent carrier with scaled bandwidth. In some examples, FFT modules1430 and IFFT modules 1460 may have different FFT points based on thehierarchical layer of a particular symbol. In some examples, legacy 20MHz symbols may have a 2048 point FFT, and burst 20 MHz symbols may havea 256 point FFT. In examples where burst mode symbols may have scaledbandwidth, the FFT size may be increased accordingly to, for example, a2048 point FFT for a 160 MHz carrier bandwidth.

Turning next to FIG. 15, a block diagram of a multiple-inputmultiple-output (MIMO) communication system 1500 is shown including aneNB 105-e and a UE 115-e. The eNB 105-e and the UE 115-e may supportcommunications in a wireless communications system having multiplehierarchical layers. The eNB 105-e may be an example of one or moreaspects of the access points, eNBs or devices 105, 1105, and/or 1155described with reference to FIGS. 1, 7, 11A, 11B, and/or 12, while theUE 115-e may be an example of one or more aspects of the UEs or devices115, 1105, and/or 1155 described with reference to FIGS. 1, 7, 11A, 11B,and/or 13. The system 1500 may illustrate aspects of the wirelesscommunications system 100 and/or 700 described with reference to FIGS. 1and/or 7, and may support hierarchical transmissions on multiplehierarchical layers across different subsets of nodes during differenttime periods such as described above with reference to FIGS. 1-14.

The eNB 105-e may be equipped with antennas 1534-0 through 1534-x, andthe UE 115-e may be equipped with antennas 1552-0 through 1552-n. In thesystem 1500, the eNB 105-e may be able to send data over multiplecommunication links at the same time. Each communication link may becalled a “layer” and the “rank” of the communication link may indicatethe number of layers used for communication. For example, in a 2×2 MIMOsystem where eNB 105-e transmits two “layers,” the rank of thecommunication link between the eNB 105-e and the UE 115-e may be two.

At the eNB 105-e, a transmit (Tx) processor 1520 may receive data from adata source. The transmit processor 1520 may process the data. Thetransmit processor 1520 may also generate reference symbols and/or acell-specific reference signal. A transmit (Tx) MIMO processor 1530 mayperform spatial processing (e.g., precoding) on data symbols, controlsymbols, and/or reference symbols, if applicable, and may provide outputsymbol streams to the transmit (Tx) modulators 1532-0 through 1532-x.Each modulator 1532 may process a respective output symbol stream (e.g.,for OFDM, etc.) to obtain an output sample stream. Each modulator 1532may further process (e.g., convert to analog, amplify, filter, andupconvert) the output sample stream to obtain a downlink (DL) signal. Inone example, DL signals from modulators 1532-0 through 1532-x may betransmitted via the antennas 1534-0 through 1534-x, respectively.

At the UE 115-e, the antennas 1552-0 through 1552-n may receive the DLsignals from the eNB 105-e and may provide the received signals to thereceive (Rx) demodulators 1554-0 through 1554-n, respectively. Eachdemodulator 1554 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 1554 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 1556 may obtainreceived symbols from all the demodulators 1554-0 through 1554-n,perform MIMO detection on the received symbols if applicable, andprovide detected symbols. A receive (Rx) processor 1558 may process(e.g., demodulate, deinterleave, and decode) the detected symbols,providing decoded data for the UE 115-e to a data output, and providedecoded control information to a processor 1580, or memory 1582. Theprocessor 1580 may include a module or function 1581 that may performvarious functions related to hierarchical transmissions on multiplehierarchical layers in a wireless communications system. For example,the module or function 1581 may perform some or all of the functions ofthe layer configuration module 1120 or 1160 described with reference toFIG. 11A or 11B, and/or of the eNB layer configuration module 1270described with reference to FIG. 12.

On the uplink (UL), at the UE 115-e, a transmit (Tx) processor 1564 mayreceive and process data from a data source. The transmit processor 1564may also generate reference symbols for a reference signal. The symbolsfrom the transmit processor 1564 may be precoded by a transmit (Tx) MIMOprocessor 1566 if applicable, further processed by the transmit (Tx)modulators 1554-0 through 1554-n (e.g., for SC-FDMA, etc.), and betransmitted to the eNB 105-e in accordance with the transmissionparameters received from the eNB 105-e. At the eNB 105-e, the UL signalsfrom the UE 115-e may be received by the antennas 1534, processed by thereceiver (Rx) demodulators 1532, detected by a MIMO detector 1536 ifapplicable, and further processed by a receive (Rx) processor 1538. Thereceive processor 1538 may provide decoded data to a data output and tothe processor 1540. The processor 1540 may include a module or function1541 that may perform various aspects related to hierarchicaltransmissions on multiple hierarchical layers in a wirelesscommunications system. For example, the module or function 1541 mayperform some or all of the functions of the layer configuration module1120 or 1160 described with reference to FIG. 11A or 11B, and/or of theUE layer configuration module 1340 described with reference to FIG. 13.

The components of the eNB 105-e may, individually or collectively, beimplemented with one or more ASICs adapted to perform some or all of theapplicable functions in hardware. Each of the noted modules may be ameans for performing one or more functions related to operation of thesystem 1500. Similarly, the components of the UE 115-e may, individuallyor collectively, be implemented with one or more ASICs adapted toperform some or all of the applicable functions in hardware. Each of thenoted components may be a means for performing one or more functionsrelated to operation of the system 1500.

In one configuration, the eNB 105-e includes means for configuring tooperate within a wireless communications system that is partiallydefined through a first layer having first layer transmissions that havea first subframe type having a first round trip time (RTT) betweentransmission and acknowledgment of receipt of the transmission, andmeans for operating at a second layer multiplexed with the first layer,the second layer transmissions having a second subframe type having asecond RTT that is less than the first RTT. In one aspect, theaforementioned means may be the eNB controller/processor 1540, the eNBmemory 1542, the eNB transmit processor 1520, eNB receiver processor1538, the eNB modulators/demodulators 1532, and the eNB antennas 1534 ofthe eNB 105-e configured to perform the functions recited by theaforementioned means. In configurations, the UE 115-e includes means forconfiguring to operate within a wireless communications system that ispartially defined through a first layer having first layer transmissionsthat have a first subframe type having a first round trip time (RTT)between transmission and acknowledgment of receipt of the transmission,and means for operating at a second layer multiplexed with the firstlayer, the second layer transmissions having a second subframe typehaving a second RTT that is less than the first RTT. The aforementionedmeans may be the UE controller/processor 1580, the UE memory 1582, theUE transmit processor 1564, UE receiver processor 1558, the UEmodulators/demodulators 1554, and the UE antennas 1552 of the UE 115-econfigured to perform the functions recited by the aforementioned means.

In another configuration, the eNB 105-e includes means for concurrentlytransmitting, in a frame, one or more subframes having a first subframetype using two or more separate carriers, at least one of the carriershaving a first bandwidth, and means for transmitting, in the frame, asubframe of a second subframe type using one carrier having a secondbandwidth, the second bandwidth being greater than the first bandwidth.In one aspect, the aforementioned means may be the eNBcontroller/processor 1540, the eNB memory 1542, the eNB transmitprocessor 1520, eNB receiver processor 1538, the eNBmodulators/demodulators 1532, and the eNB antennas 1534 of the eNB 105-econfigured to perform the functions recited by the aforementioned means.In configurations, the UE 115-e includes means for concurrentlytransmitting, in a frame, one or more subframes having a first subframetype using two or more separate carriers, at least one of the carriershaving a first bandwidth, and means for transmitting, in the frame, asubframe of a second subframe type using one carrier having a secondbandwidth, the second bandwidth being greater than the first bandwidth.The aforementioned means may be the UE controller/processor 1580, the UEmemory 1582, the UE transmit processor 1564, UE receiver processor 1558,the UE modulators/demodulators 1554, and the UE antennas 1552 of the UE115-e configured to perform the functions recited by the aforementionedmeans.

FIG. 16 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure. For clarity, the method 1600 is described below withreference to ones of the access points, eNBs, UEs, or devices 105, 115,1105, and/or 1155 described with reference to FIGS. 1, 7, 11A, 11B, 12,13, and/or 15. In one example, an eNB, UE, or device may execute one ormore sets of codes to control the functional elements of the eNB, UE, ordevice to perform the functions described below.

At block 1605, an eNB, UE, and/or device may be configured to operatewithin a wireless communications system, the system partially definedthrough a first layer with first layer transmissions having a firstsubframe type having a first RTT between transmission and acknowledgmentof receipt of the transmission. The operation(s) at block 1605 may insome cases be performed using the layer configuration module 1120 and/or1160 described with reference to FIGS. 11A and/or 11B, the eNB layerconfiguration module 1270 described with reference to FIG. 12, the UElayer configuration module 1340 described with reference to FIG. 13, theprocessor 1580 and/or the processor 1540 and related componentsdescribed with reference to FIG. 15.

At block 1610, the eNB, UE, and/or device may operate at a second layermultiplexed with the first layer, second layer transmissions having asecond subframe type having a second RTT that is less than the firstRTT. The operation(s) at block 1610 may in some cases be performed usinglayer configuration module 1120 and/or 1160 in conjunction with receivermodules 1110 and transmitter modules 1130, described with reference toFIGS. 11A and/or 11B, the eNB layer configuration module 1270 inconjunction with transceiver module(s) 1255 and antenna(s) 1260,described with reference to FIG. 12, the UE layer configuration module1340 in conjunction with transceiver module(s) 1370 and antenna(s) 1380,described with reference to FIG. 13, the processor 1580 and/or theprocessor 1540 and related components described with reference to FIG.15.

Thus, the method 1600 may provide for wireless communications indifferent hierarchical layers in which RTTs for the second layer areshorter than RTTs for the first layer, and may thus provide a secondlayer with enhanced TCP segment error rates and thereby enhanced datatransfer rates. It should be noted that the method 1600 is just oneimplementation and that the operations of the method 1600 may berearranged or otherwise modified such that other implementations arepossible.

FIG. 17 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure. For clarity, the method 1700 is described below withreference to ones of the access points, eNBs, UEs, or devices 105, 115,1105, and/or 1155 described with reference to FIGS. 1, 7, 11A, 11B, 12,13, and/or 15. In one example, an eNB, UE, or device may execute one ormore sets of codes to control the functional elements of the eNB, UE, ordevice to perform the functions described below.

At block 1705, an eNB, UE, and/or device may configure a first layeroperation with first layer transmissions having a first subframe typehaving a first RTT between transmission and acknowledgment of receipt ofthe transmission. The operation(s) at block 1705 may in some cases beperformed using the layer configuration module 1120 and/or 1160 inconjunction with first layer configuration module 1170 described withreference to FIGS. 11A and/or 11B, the eNB layer configuration module1270 in conjunction with eNB first layer configuration module 1280described with reference to FIG. 12, the UE layer configuration module1340 in conjunction with UE first layer configuration module 1350described with reference to FIG. 13, the processor 1580 and/or theprocessor 1540 and related components described with reference to FIG.15.

At block 1710, the eNB, UE, and/or device may configure second layeroperation with second layer transmissions having a second subframe typehaving a second RTT that is less than the first RTT. The operation(s) atblock 1710 may in some cases be performed using layer configurationmodule 1120 and/or 1160 in conjunction with burst mode module 1175described with reference to FIGS. 11A and/or 11B, the eNB layerconfiguration module 1270 in conjunction with eNB burst mode module 1285described with reference to FIG. 12, the UE layer configuration module1340 in conjunction with UE burst mode module 1355 described withreference to FIG. 13, the processor 1580 and/or the processor 1540 andrelated components described with reference to FIG. 15.

At block 1715, the eNB, UE, and/or device may transmit one or moresubframes having the first subframe type. The operation(s) at block 1715may in some cases be performed using layer configuration module 1120and/or 1160 in conjunction with first layer configuration module 1170and transmitter modules 1130, described with reference to FIGS. 11Aand/or 11B, the eNB layer configuration module 1270 in conjunction witheNB first layer configuration module 1280, transceiver module(s) 1255and antenna(s) 1260, described with reference to FIG. 12, the UE layerconfiguration module 1340 in conjunction with UE first layerconfiguration module 1350, transceiver module(s) 1370 and antenna(s)1380, described with reference to FIG. 13, the processor 1580 and/or theprocessor 1540 and related components described with reference to FIG.15.

At block 1720, the eNB, UE, and/or device may transmit one or moresubframes having the second subframe type that are time divisionmultiplexed with the one or more subframes of the first subframe type.The operation(s) at block 1720 may in some cases be performed usinglayer configuration module 1120 and/or 1160 in conjunction with burstmode module 1175 and transmitter modules 1130, described with referenceto FIGS. 11A and/or 11B, the eNB layer configuration module 1270 inconjunction with eNB burst mode module 1285, transceiver module(s) 1255,and antenna(s) 1260, described with reference to FIG. 12, the UE layerconfiguration module 1340 in conjunction with UE burst mode module 1355,transceiver module(s) 1370, and antenna(s) 1380, described withreference to FIG. 13, the processor 1580 and/or the processor 1540 andrelated components described with reference to FIG. 15.

Thus, the method 1700 may provide for wireless communications indifferent hierarchical layers in which RTTs for the second layer areshorter than RTTs for the first layer, and may thus provide a secondlayer with enhanced TCP segment error rates and thereby enhanced datatransfer rates. It should be noted that the method 1700 is just oneimplementation and that the operations of the method 1700 may berearranged or otherwise modified such that other implementations arepossible.

FIG. 18 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure. For clarity, the method 1800 is described below withreference to ones of the access points, eNBs, UEs, or devices 105, 115,1105, and/or 1155 described with reference to FIGS. 1, 7, 11A, 11B, 12,13, and/or 15. In one example, an eNB, UE, or device may execute one ormore sets of codes to control the functional elements of the eNB, UE, ordevice to perform the functions described below.

At block 1805, an eNB, UE, and/or device may configure a first layeroperation with first layer transmissions having a first subframe typehaving a first RTT between transmission and acknowledgment of receipt ofthe transmission. The operation(s) at block 1805 may in some cases beperformed using the layer configuration module 1120 and/or 1160 inconjunction with first layer configuration module 1170 described withreference to FIGS. 11A and/or 11B, the eNB layer configuration module1270 in conjunction with eNB first layer configuration module 1280described with reference to FIG. 12, the UE layer configuration module1340 in conjunction with UE first layer configuration module 1350described with reference to FIG. 13, the processor 1580 and/or theprocessor 1540 and related components described with reference to FIG.15.

At block 1810, the eNB, UE, and/or device may configure second layeroperation with second layer transmissions having a second subframe typehaving a second RTT that is less than the first RTT. The operation(s) atblock 1810 may in some cases be performed using layer configurationmodule 1120 and/or 1160 in conjunction with burst mode module 1175described with reference to FIGS. 11A and/or 11B, the eNB layerconfiguration module 1270 in conjunction with eNB burst mode module 1285described with reference to FIG. 12, the UE layer configuration module1340 in conjunction with UE burst mode module 1355 described withreference to FIG. 13, the processor 1580 and/or the processor 1540 andrelated components described with reference to FIG. 15.

At block 1815, the eNB, UE, and/or device may transmit data in asubframe of the second subframe type. The operation(s) at block 1815 mayin some cases be performed using layer configuration module 1120 and/or1160 in conjunction with burst mode module 1175 and transmitter modules1130, described with reference to FIGS. 11A and/or 11B, the eNB layerconfiguration module 1270 in conjunction with eNB burst mode module1285, transceiver module(s) 1255, and antenna(s) 1260, described withreference to FIG. 12, the UE layer configuration module 1340 inconjunction with UE burst mode module 1355, transceiver module(s) 1370,and antenna(s) 1380, described with reference to FIG. 13, the processor1580 and/or the processor 1540 and related components described withreference to FIG. 15.

At block 1820, the eNB, UE, and/or device may receive acknowledgment ofreceipt of the transmission within the subframe of the second subframetype. The operation(s) at block 1820 may in some cases be performedusing layer configuration module 1120 and/or 1160 in conjunction withburst mode module 1175 and receiver modules 1110, described withreference to FIGS. 11A and/or 11B, the eNB layer configuration module1270 in conjunction with eNB burst mode module 1285, transceivermodule(s) 1255, and antenna(s) 1260, described with reference to FIG.12, the UE layer configuration module 1340 in conjunction with UE burstmode module 1355, transceiver module(s) 1370, and antenna(s) 1380,described with reference to FIG. 13, the processor 1580 and/or theprocessor 1540 and related components described with reference to FIG.15.

Thus, the method 1800 may provide for wireless communications indifferent hierarchical layers in which acknowledgment of receipt of thea transmission may be received within a same subframe as thetransmission. It should be noted that the method 1800 is just oneimplementation and that the operations of the method 1800 may berearranged or otherwise modified such that other implementations arepossible.

FIG. 19 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure. For clarity, the method 1900 is described below withreference to ones of the access points, eNBs, UEs, or devices 105, 115,1105, and/or 1155 described with reference to FIGS. 1, 7, 11A, 11B, 12,13, and/or 15. In one example, an eNB, UE, or device may execute one ormore sets of codes to control the functional elements of the eNB, UE, ordevice to perform the functions described below.

At block 1905, an eNB, UE, and/or device may concurrently transmit, in aframe, one or more subframes having a first subframe type using two ormore separate carriers, at least one of the carriers having a firstbandwidth. The operation(s) at block 1905 may in some cases be performedusing the layer configuration module 1120 and/or 1160 in conjunctionwith scalable bandwidth module 1185 and transmitter modules 1130described with reference to FIGS. 11A and/or 11B, the eNB layerconfiguration module 1270 in conjunction with eNB scalable bandwidthmodule 1295, transceiver module(s) 1255, and antenna(s) 1260, describedwith reference to FIG. 12, the UE layer configuration module 1340 inconjunction with UE scalable bandwidth configuration module 1365,transceiver module(s) 1370, and antenna(s) 1380, described withreference to FIG. 13, the processor 1580 and/or the processor 1540 andrelated components described with reference to FIG. 15.

At block 1910, the eNB, UE, and/or device may transmit, in the frame, asubframe of a second subframe type using one carrier having a secondbandwidth, the second bandwidth being greater than the first bandwidth.The operation(s) at block 1910 may in some cases be performed using thelayer configuration module 1120 and/or 1160 in conjunction with scalablebandwidth module 1185 and transmitter modules 1130 described withreference to FIGS. 11A and/or 11B, the eNB layer configuration module1270 in conjunction with eNB scalable bandwidth module 1295, transceivermodule(s) 1255, and antenna(s) 1260, described with reference to FIG.12, the UE layer configuration module 1340 in conjunction with UEscalable bandwidth configuration module 1365, transceiver module(s)1370, and antenna(s) 1380, described with reference to FIG. 13, theprocessor 1580 and/or the processor 1540 and related componentsdescribed with reference to FIG. 15.

Thus, the method 1900 may provide for wireless communications that mayutilize scalable bandwidth in different hierarchical layers. It shouldbe noted that the method 1900 is just one implementation and that theoperations of the method 1900 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 20 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure. For clarity, the method 2000 is described below withreference to ones of the access points, eNBs, UEs, or devices 105, 115,1105, and/or 1155 described with reference to FIGS. 1, 7, 11A, 11B, 12,13, and/or 15. In one example, an eNB may execute one or more sets ofcodes to control the functional elements of the eNB to perform thefunctions described below.

At block 2005, the eNB may configure a carrier with a first regionhaving a first symbol duration and a second region having a secondsymbol duration different from the first symbol duration, the first andsecond regions being TDM or FDM. In some examples, second symbolduration is shorter than the first symbol duration. The operation(s) atblock 2005 may in some cases be performed using the layer configurationmodule 1120 and/or 1160 described with reference to FIGS. 11A and/or11B, the eNB region configuration module 1297 described with referenceto FIG. 12, and/or the processor 1540 and related components describedwith reference to FIG. 15.

At block 2010, the eNB may communicate with a UE using the first orsecond region according to a latency requirement of the UE. This mayinclude transmitting a signal in a symbol of the first region, where thesignal is indicative of the second symbol duration. The signal may beRRC signaling, a broadcast message, Layer 1 signaling, MAC layersignaling, or the like. The operation(s) at block 2010 may in some casesbe performed using the receiver modules 1110 or 1110-a or transmittermodules 1130 or 1130-a of FIG. 11A or 11B, the transceiver modules 1255of FIG. 12, and/or the processor 1540 and related components FIG. 15.

In some examples, the method 1600 may also include adjusting a portionof the carrier occupied by the second region based at least in part onthe latency requirement of the UE. This may include adjusting a timeduration or periodicity of the second region; or it may includeadjusting a bandwidth of the second region. These adjusting operationsmay be performed by the clock module 1180 or scalable bandwidth module1185 of FIG. 11B, or the eNB clock module 1290 or eNB scalable bandwidthmodule 1295 of FIG. 12.

The method 2000 may also include configuring a guard band between thefirst and second regions. Additionally or alternatively, the method 2000may include configuring a third region of the carrier with the secondsymbol duration. In various examples, the first and second regions maybe FDM, and the third region may be TDM with the first and secondregions. The operations of configuring the third region or the guardband, or both, may be performed by the region configuration module 1190of FIG. 11B, eNB region configuration module 1297 of FIG. 12, or theprocessor 1540 and related components of FIG. 15.

FIG. 21 is a flowchart conceptually illustrating an example of a methodof wireless communication, in accordance with aspects of the presentdisclosure. For clarity, the method 2100 is described below withreference to ones of the access points, eNBs, UEs, or devices 105, 115,1105, and/or 1155 described with reference to FIGS. 1, 7, 11A, 11B, 12,13, and/or 15. In one example, a UE may execute one or more sets ofcodes to control the functional elements of the UE to perform thefunctions described below.

At block 2105, the UE may identify a first region having a first symbolduration. The operation(s) at block 2105 may in some cases be performedusing the layer configuration module 1120 and/or 1160 described withreference to FIGS. 11A and/or 11B, the UE region configuration module1367 described with reference to FIG. 13, and/or the processor 1580 andrelated components described with reference to FIG. 15.

At block 2110, the UE may identify a second region having a secondsymbol duration different from the first symbol duration, the first andsecond regions being TDM or FDM. In some examples, second symbolduration is shorter than the first symbol duration. The operation(s) atblock 2105 may in some cases be performed using the layer configurationmodule 1120 and/or 1160 described with reference to FIGS. 11A and/or11B, the UE region configuration module 1367 described with reference toFIG. 13, and/or the processor 1580 and related components described withreference to FIG. 15.

At block 2115, the UE may communicate with a base station using thefirst or second region based at least in part on a latency requirement.This may include receiving a signal in a symbol of the first region,where the signal is indicative of the second symbol duration. The signalmay be RRC signaling, a broadcast message, Layer 1 signaling, MAC layersignaling, or the like. The operation(s) at block 2115 may in some casesbe performed using the receiver modules 1110 or 1110-a or transmittermodules 1130 or 1130-a of FIG. 11A or 11B, the transceiver modules 1370of FIG. 12, and/or the processor 1580 and related components FIG. 15.

In some examples, the method 2100 may also include identifying a guardband between the first and second regions. Additionally oralternatively, the method 2100 may include identifying a third region ofthe carrier with the second symbol duration. In various examples, thefirst and second regions may be FDM, and the third region may be TDMwith the first and second regions. The operations of identifying thethird region or the guard band, or both, may be performed by the regionconfiguration module 1190 of FIG. 11B, UE region configuration module1367 of FIG. 13, or the processor 1580 and related components of FIG.15.

The detailed description set forth above in connection with the appendeddrawings describes exemplary embodiments and does not represent the onlyexamples that may be implemented or that are within the scope of theclaims. The term “exemplary” used throughout this description means“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand devices are shown in block diagram form in order to avoid obscuringthe concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope and spirit of the disclosure and appended claims. For example,due to the nature of software, functions described above can beimplemented using software executed by a processor, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions may also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. Also, as used herein, including in theclaims, “or” as used in a list of items prefaced by “at least one of”indicates a disjunctive list such that, for example, a list of “at leastone of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., Aand B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method of wireless communication, comprising:configuring a single frame structure of a single carrier with a firstregion having a first symbol duration and a second region having asecond symbol duration different from the first symbol duration, whereinthe first and second regions of the single frame structure of the singlecarrier are time-division multiplexed (TDM) or frequency-divisionmultiplexed (FDM), wherein the first region includes a control channeland a shared channel, and the second region includes a control channeland a shared channel, and wherein the second region includes bothdownlink symbols and uplink symbols, and wherein the second symbolduration is configurable; and communicating with a user equipment (UE)using the first or second region of the single frame structure of thesingle carrier.
 2. The method of claim 1, further comprising: adjustinga portion of the single frame structure of the single carrier occupiedby the second region based at least in part on a latency requirement ofthe UE.
 3. The method of claim 2, wherein the first and second regionsare TDM, and wherein adjusting the portion of the single frame structureof the single carrier occupied by the second region comprises: adjustinga time duration or periodicity of the second region.
 4. The method ofclaim 2, wherein the first and second regions are FDM, and whereinadjusting the portion of the single frame structure of the singlecarrier occupied by the second region comprises: adjusting a bandwidthof the second region.
 5. The method of claim 4, further comprising:configuring a guard band between the first and second regions.
 6. Themethod of claim 1, wherein configuring the single frame structure of thesingle carrier comprises: transmitting a signal in a symbol of the firstregion, the signal indicative of the second symbol duration andcomprising at least one of radio resource control (RRC) signaling, abroadcast message, Layer 1 signaling, or a media access control (MAC)layer signaling.
 7. The method of claim 1, further comprising:configuring a third region of the single frame structure of the singlecarrier, the third region having the second symbol duration, wherein thefirst and second regions are FDM, and wherein the third region is TDMwith the first and second regions.
 8. The method of claim 7, furthercomprising: configuring a guard band between the first and secondregions.
 9. The method of claim 1, wherein the second symbol duration isshorter than the first symbol duration.
 10. The method of claim 1,wherein the shared channel of the first region comprises a firstphysical downlink shared channel (PDSCH), and the control channel of thefirst region comprises a first physical downlink control channel(PDCCH); and wherein the shared channel of the second region comprises asecond physical downlink shared channel (PDSCH), and the control channelof the second region comprises a second physical downlink controlchannel (PDCCH).
 11. The method of claim 1, wherein the first region hasa first bandwidth and wherein the second region has a second bandwidthdifferent from the first bandwidth.
 12. A method of wirelesscommunication, comprising: identifying a first region of a single framestructure of a single carrier, the first region having a first symbolduration; identifying a second region of the single frame structure ofthe single carrier, the second region having a second symbol durationdifferent from the first symbol duration, wherein the first and secondregions of the single frame structure of the single carrier aretime-division multiplexed (TDM) or frequency-division multiplexed (FDM),wherein the first region includes a control channel and a sharedchannel, and the second region includes a control channel and a sharedchannel, and wherein the second region includes both downlink symbolsand uplink symbols, and wherein the second symbol duration isconfigurable; and communicating with a base station using the first orsecond region of the single frame structure of the single carrier. 13.The method of claim 12, wherein the first and second regions are FDM,and wherein the method further comprises: identifying a guard bandbetween the first and second regions.
 14. The method of claim 12,wherein identifying the second region of the single frame structure ofthe single carrier comprises: receiving a signal in a symbol of thefirst region, the signal indicative of the second symbol duration andcomprising at least one of radio resource control (RRC) signaling, abroadcast message, Layer 1 signaling, or a media access control (MAC)layer signaling.
 15. The method of claim 12, further comprising:identifying a third region of the single frame structure of the singlecarrier, the third region having the second symbol duration, wherein thefirst and second regions are FDM and wherein the third region is TDMwith the first and second regions.
 16. The method of claim 15, furthercomprising: identifying a guard band between the first and secondregions.
 17. The method of claim 12, wherein the second symbol durationis shorter than the first symbol duration.
 18. The method of claim 12,wherein the first region has a 15 kHz subcarrier spacing, and the secondregion has a 60 kHz or 120 kHz subcarrier spacing.
 19. The method ofclaim 12, wherein the first region is a first subframe of the singleframe structure, and the second region is a second subframe of thesingle frame structure that is different than the first subframe;wherein the first subframe comprises a first number of orthogonalfrequency division multiplexing (OFDM) symbols, and the second subframecomprises a second number of OFDM symbols that is different from thefirst number of OFDM symbols; and wherein each of the OFDM symbols inthe first subframe have the first symbol duration, and each of the OFDMsymbols in the second subframe have the second symbol duration that isdifferent than the first symbol duration.
 20. The method of claim 12,wherein the first region has a first bandwidth and wherein the secondregion has a second bandwidth different from the first bandwidth.
 21. Anapparatus for wireless communication, comprising: a processor; memory inelectronic communication with the processor; and instructions stored inthe memory, the instructions executable by the processor to cause theapparatus to: configure a single frame structure of a single carrierwith a first region having a first symbol duration and a second regionhaving a second symbol duration different from the first symbolduration, wherein the first and second regions of the single framestructure of the single carrier are time-division multiplexed (TDM) orfrequency-division multiplexed (FDM), wherein the first region includesa control channel and a shared channel, and the second region includes acontrol channel and a shared channel, and wherein the second regionincludes both downlink symbols and uplink symbols, and wherein thesecond symbol duration is configurable; and communicate with a userequipment (UE) using the first or second region of the single framestructure of the single carrier.
 22. The apparatus of claim 21, whereinthe instructions are executable by the processor to cause the apparatusto: adjust a portion of the single frame structure of the single carrieroccupied by the second region based at least in part on a latencyrequirement of the UE.
 23. The apparatus of claim 22, wherein the firstand second regions are TDM, and wherein the instructions are executableby the processor to cause the apparatus to: adjust a time duration orperiodicity of the second region.
 24. The apparatus of claim 22, whereinthe first and second regions are FDM, and wherein the instructions areexecutable by the processor to cause the apparatus to: adjust abandwidth of the second region.
 25. The apparatus of claim 24, whereinthe instructions are executable by the processor to cause the apparatusto: configure a guard band between the first and second regions.
 26. Theapparatus of claim 21, wherein the instructions are executable by theprocessor to cause the apparatus to: transmit a signal in a symbol ofthe first region, the signal indicative of the second symbol durationand comprising at least one of radio resource control (RRC) signaling, abroadcast message, Layer 1 signaling, or a media access control (MAC)layer signaling.
 27. The apparatus of claim 21, wherein the instructionsare executable by the processor to cause the apparatus to: configure athird region of the single frame structure of the single carrier, thethird region having the second symbol duration, wherein the first andsecond regions are FDM, and wherein the third region is TDM with thefirst and second regions.
 28. The apparatus of claim 27, wherein theinstructions are executable by the processor to cause the apparatus to:configure a guard band between the first and second regions.
 29. Theapparatus of claim 21, wherein the second symbol duration is shorterthan the first symbol duration.
 30. An apparatus for wirelesscommunication, comprising: a processor; memory in electroniccommunication with the processor; and instructions stored in the memory,the instructions executable by the processor to cause the apparatus to:identify a first region of a single frame structure of a single carrier,the first region having a first symbol duration; identify a secondregion of the single frame structure of the single carrier, the secondregion having a second symbol duration different from the first symbolduration, wherein the first and second regions of the single framestructure of the single carrier are time-division multiplexed (TDM) orfrequency-division multiplexed (FDM), wherein the first region includesa control channel and a shared channel, and the second region includes acontrol channel and a shared channel, and wherein the second regionincludes both downlink symbols and uplink symbols, and wherein thesecond symbol duration is configurable; and communicate with a basestation using the first or second region of the single frame structureof the single carrier.
 31. The apparatus of claim 30, wherein the firstand second regions are FDM, and wherein the instructions are executableby the processor to cause the apparatus to: identify a guard bandbetween the first and second regions.
 32. The apparatus of claim 30,wherein the instructions are executable by the processor to cause theapparatus to: receive a signal in a symbol of the first region, thesignal indicative of the second symbol duration and comprising at leastone of radio resource control (RRC) signaling, a broadcast message,Layer 1 signaling, or a media access control (MAC) layer signaling. 33.The apparatus of claim 30, wherein the instructions are executable bythe processor to cause the apparatus to: identify a third region of thesingle frame structure of the single carrier, the third region havingthe second symbol duration, wherein the first and second regions are FDMand wherein the third region is TDM with the first and second regions.34. The apparatus of claim 33, wherein the instructions are executableby the processor to cause the apparatus to: identify a guard bandbetween the first and second regions.
 35. The apparatus of claim 30,wherein the second symbol duration is shorter than the first symbolduration.